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Abstract:

The disclosure relates to handover optimization in a voice communication
session or other real-time multimedia session. For example, a wireless
device associated with a parent user may detect a condition triggering a
handover during a current voice communication session between the parent
user and a target user, wherein the handover has a type associated with a
switching delay. The wireless device may maintain statistics relating to
an average mutual silence duration after talk spurts from the parent user
and the target user based on one or more past voice communication
sessions in which at least the parent user participated and trigger the
handover when a next talk spurt from either the parent user or the target
user ends where the average mutual silence duration exceeds the switching
delay associated with the handover type.

Claims:

1. A method for optimizing handover during voice sessions, comprising:
detecting a condition triggering a handover at a wireless device
associated with a parent user during a current voice communication
session between the parent user and a target user, wherein the handover
has a type associated with a switching delay; determining an average
mutual silence duration after talk spurts from the parent user and the
target user based on one or more past voice communication sessions in
which at least the parent user participated; and triggering the handover
when a next talk spurt from either the parent user or the target user
ends in response to the determined average mutual silence duration
exceeding the switching delay associated with the handover type.

2. The method recited in claim 1, wherein the target user further
participated in the one or more past voice communication sessions used to
determine the average mutual silence duration.

3. The method recited in claim 2, wherein triggering the handover
comprises: determining whether the parent user or the target user spoke
more often in the one or more past voice communication sessions;
triggering the handover after the next talk spurt from the parent user in
response to determining that the parent user spoke more often in the one
or more past voice communication sessions; and triggering the handover
after the next talk spurt from the target user in response to determining
that the target user spoke more often in the one or more past voice
communication sessions.

4. The method recited in claim 3, further comprising: determining that
the current voice communication session has ended; and updating one or
more statistics that indicate the average mutual silence duration after
the talk spurts from the parent user and the target user and that further
indicate how often the parent user and the target user speak in voice
communication sessions with one another based on the ended current voice
communication session.

5. The method recited in claim 2, wherein the handover is triggered after
the next talk spurt from either user in response to determining that the
parent user and the target user spoke at approximately the same frequency
in the one or more past voice communication sessions.

6. The method recited in claim 1, further comprising: storing one or more
statistics that relate to the switching delay associated with the
handover type and switching delays associated with one or more additional
handover types, wherein handover types in which the wireless device
switches from a current radio access technology (RAT) to a target RAT
have greater switching delays than intra-RAT handover types.

7. The method recited in claim 6, further comprising: determining that
the triggered handover succeeded; and updating the one or more statistics
that relate to the switching delay associated with the handover type
according to a switching delay associated with the successfully triggered
handover.

8. The method recited in claim 1, wherein determining the average mutual
silence duration comprises: calculating average mutual silence durations
after talk spurts from the parent user and one or more other target users
that participated in the one or more past voice communication sessions
with the parent user in response to the parent user not having any past
voice communication sessions with the target user.

9. The method recited in claim 1, further comprising: allowing a modem on
the wireless device to make a decision about when to trigger the handover
in response to determining that the average mutual silence duration does
not exceed the switching delay associated with the handover type.

10. The method recited in claim 1, further comprising: sending a talk
burst request from the parent user to a server that mediates the voice
communication session between the parent user and the target user;
receiving a talk burst queue position status message from the server,
wherein the received talk burst queue position status message indicates
that the target user has permission to send a current talk burst and
further indicates a position that the talk burst request from the parent
user holds in a talk burst queue; and receiving a command to trigger or
delay the handover based on the talk burst queue position status message.

11. The method recited in claim 10, wherein the received talk burst queue
position status message further indicates positions that talk burst
requests from other target users participating in the voice communication
session hold in the talk burst queue.

12. The method recited in claim 1, wherein the current voice
communication session and the one or more past voice communication
sessions comprise one or more of push-to-talk (PTT) or full-duplex Voice
over Internet Protocol (VoIP) sessions.

13. A wireless device, comprising: a storage device configured to store
statistics associated with one or more past voice communication sessions
in which at least a parent user associated with the wireless device
participated; and one or more processors configured to: detect a
condition triggering a handover during a current voice communication
session between the parent user and a target user, wherein the handover
has a type associated with a switching delay; determine, from the stored
statistics, an average mutual silence duration after talk spurts from the
parent user and the target user based on one or more past voice
communication sessions in which at least the parent user participated;
and trigger the handover when a next talk spurt from either the parent
user or the target user ends in response to the determined average mutual
silence duration exceeding the switching delay associated with the
handover type.

14. The wireless device recited in claim 13, wherein the statistics
stored in the storage device comprise: statistics associated with one or
more past voice communication sessions between the parent user and the
target user, and statistics that relate to the switching delay associated
with the handover type and one or more additional handover types, wherein
handover types in which the wireless device switches from a current radio
access technology (RAT) to a target RAT have greater switching delays
than intra-RAT handover types.

15. The wireless device recited in claim 14, wherein the one or more
processors are further configured to trigger the handover after the next
talk spurt from the parent user in response to the stored statistics
indicating that the parent user spoke more often in the one or more past
voice communication sessions.

16. The wireless device recited in claim 14, wherein the one or more
processors are further configured to trigger the handover after the next
talk spurt from the target user in response to the stored statistics
indicating that the target user spoke more often in the one or more past
voice communication sessions.

17. The wireless device recited in claim 14, wherein the one or more
processors are further configured to trigger the handover after the next
talk spurt from either user in response to the stored statistics
indicating that the parent user and the target user spoke at
approximately the same frequency in the one or more past voice
communication sessions.

18. The wireless device recited in claim 14, wherein the one or more
processors are further configured to update the statistics that relate to
the switching delay associated with the handover type according to a
switching delay associated with the triggered handover.

19. The wireless device recited in claim 13, further comprising: a
transmitter configured to send a talk burst request from the parent user
to a server that mediates the voice communication session between the
parent user and the target user; and a receiver configured to: receive a
talk burst queue position status message from the server, wherein the
received talk burst queue position status message indicates that the
target user has permission to send a current talk burst and further
indicates a position that the talk burst request from the parent user
holds in a talk burst queue; and receive a command to trigger or delay
the handover based on the talk burst queue position status message.

20. The wireless device recited in claim 19, wherein the received talk
burst queue position status message further indicates positions that talk
burst requests from other target users participating in the voice
communication session hold in the talk burst queue.

21. A wireless device, comprising: means for detecting a condition
triggering a handover during a current voice communication session
between a parent user associated with the wireless device and a target
user, wherein the handover has a type associated with a switching delay;
means for determining an average mutual silence duration after talk
spurts from the parent user and the target user based on one or more past
voice communication sessions in which at least the parent user
participated; and means for triggering the handover when a next talk
spurt from either the parent user or the target user ends in response to
the determined average mutual silence duration exceeding the switching
delay associated with the handover type.

22. The wireless device recited in claim 21, wherein the means for
triggering the handover comprises: means for triggering the handover
after the next talk spurt from the parent user in response to determining
that the target user further participated in the one or more past voice
communication sessions used to determine the average mutual silence
duration and the parent user spoke more often in the one or more past
voice communication sessions.

23. The wireless device recited in claim 21, wherein the means for
triggering the handover comprises: means for triggering the handover
after the next talk spurt from the target user in response to determining
that the target user further participated in the one or more past voice
communication sessions used to determine the average mutual silence
duration and the target user spoke more often in the one or more past
voice communication sessions.

24. The wireless device recited in claim 21, wherein the means for
triggering the handover comprises: means for triggering the handover
after the next talk spurt from either user in response to determining
that the target user further participated in the one or more past voice
communication sessions used to determine the average mutual silence
duration and the parent user and the target user spoke at approximately
the same frequency in the one or more past voice communication sessions.

25. The wireless device recited in claim 21, further comprising: means
for updating one or more statistics that indicate the average mutual
silence duration after the talk spurts from the parent user and the
target user and how often the parent user and the target user speak in
voice communication sessions with one another after the current voice
communication session ends.

26. The wireless device recited in claim 21, wherein the determined
average mutual silence duration comprises an average mutual silence
duration after talk spurts from the parent user and one or more other
target users that participated in the one or more past voice
communication sessions with the parent user if the parent user does not
have any past voice communication sessions with the target user.

27. The wireless device recited in claim 21, further comprising: means
for storing one or more statistics that relate to the switching delay
associated with the handover type and switching delays associated with
one or more additional handover types, wherein handover types in which
the wireless device switches from a current radio access technology (RAT)
to a target RAT have greater switching delays than intra-RAT handover
types.

28. The wireless device recited in claim 27, further comprising: means
for updating the one or more statistics that relate to the switching
delay associated with the handover type according to a switching delay
associated with the triggered handover.

29. The wireless device recited in claim 21, further comprising: means
for sending a talk burst request from the parent user to a server that
mediates the voice communication session between the parent user and the
target user; means for receiving a talk burst queue position status
message from the server, wherein the received talk burst queue position
status message indicates that the target user has permission to send a
current talk burst and further indicates a position that the talk burst
request from the parent user holds in a talk burst queue; and means for
receiving a command to trigger or delay the handover based on the talk
burst queue position status message.

30. A computer-readable storage medium having computer-executable
instructions recorded thereon, wherein executing the computer-executable
instructions on a wireless device causes the wireless device to: detect a
condition triggering a handover during a current voice communication
session between a parent user associated with the wireless device and a
target user, wherein the handover has a type associated with a switching
delay; determine an average mutual silence duration after talk spurts
from the parent user and the target user based on one or more past voice
communication sessions in which at least the parent user participated;
and trigger the handover when a next talk spurt from either the parent
user or the target user ends in response to the determined average mutual
silence duration exceeding the switching delay associated with the
handover type.

Description:

TECHNICAL FIELD

[0001] The disclosure relates to wireless group communications, and in
particular, to radio access technology (RAT) handover optimization in a
push-to-talk (PTT) session.

BACKGROUND

[0002] Wireless communication systems have developed through various
generations, including a first-generation analog wireless phone service
(1G), a second-generation (2G) digital wireless phone service (including
interim 2.5G and 2.75G networks) and third-generation (3G) and
fourth-generation (4G) high speed data/Internet-capable wireless
services. There are presently many different types of wireless
communication systems in use, including Cellular and Personal
Communications Service (PCS) systems. Exemplary cellular systems include
the cellular Analog Advanced Mobile Phone System (AMPS), digital cellular
systems based on Code Division Multiple Access (CDMA), Frequency Division
Multiple Access (FDMA), Time Division Multiple Access (TDMA), the Global
System for Mobile access (GSM) variation of TDMA, and newer hybrid
digital communication systems using both TDMA and CDMA technologies. More
recently, Long Term Evolution (LTE) has been developed as a wireless
communications protocol for mobile phones and other terminals to
communicate data at high speeds. LTE is based on GSM, and includes
contributions from various GSM-related protocols such as Enhanced Data
rates for GSM Evolution (EDGE) and Universal Mobile Telecommunications
System (UMTS) protocols such as High-Speed Packet Access (HSPA).

[0003] Accordingly, communications systems and devices are becoming
increasingly diverse with new technological advancements. Communications
devices are now able to support various different communications
technologies and protocols. For example, a wireless telecommunication
service generically referred to as "Push-To-Talk" (PTT) capability can
provide quick one-to-one or one-to-many communications, wherein a carrier
typically establishes the recipient devices for wireless device
communicating in a PTT group. For example, a PTT communication connection
may typically be initiated in response to a single button-push on a
wireless device, which may activate a half-duplex link between the
speaker and each member device within the group, wherein the device can
subsequently receive incoming PTT transmissions once the button is
released. In some arrangements, the PTT speaker will have the "floor"
whereby no other group member can speak while the speaker holds the
floor. Accordingly, once the speaker holding the floor releases the PTT
button, any other individual member within the group can engage a PTT
button in order to request and thereby take the floor. Furthermore, other
wireless communication services may support full-duplex
Voice-over-Internet Protocol (VoIP) sessions, where communication may be
allowed in both directions such that different parties can communicate
simultaneously (i.e., parties on different ends can speak and be heard at
the same time).

[0004] However, various conditions may result in a user involved in a
half-duplex or full-duplex voice call needing to trigger a handover from
a current base station to a target base station in the same access
network or a different access network (e.g., user mobility, radio
conditions, cell capacity, more favorable conditions in a neighbor cell,
etc.). In the former case, because the current base station and the
target base station are in the same access network and therefore
implement the same radio access technology (RAT), the handover may be
termed an "intra-RAT" handover. In the latter case, the base stations in
different access networks may implement different RATs, in which case the
handover may be termed an "inter-RAT" handover. However, in cases where
the current and target base stations are in different access networks but
implement the same RAT, the handover would also be an intra-RAT handover.
In any case, if a wireless device is involved in a half-duplex or
full-duplex voice call and a handover is triggered, the voice call may
end if the handover delay results in inactivity leading to a dropped call
and/or perceivable "clicks" due to packet loss and/or delays during the
handover may result. Accordingly, depending on the target access network,
handovers that are triggered while a wireless device is involved in a
voice call or other real-time multimedia session may cause session
interruption, packet delay, packet loss, and degraded user experience,
among other problems.

SUMMARY

[0005] The following presents a simplified summary relating to one or more
aspects and/or embodiments disclosed herein. As such, the following
summary should not be considered an extensive overview relating to all
contemplated aspects and/or embodiments, nor should the following summary
be regarded to identify key or critical elements relating to all
contemplated aspects and/or embodiments or to delineate the scope
associated with any particular aspect and/or embodiment. Accordingly, the
following summary has the sole purpose to present certain concepts
relating to one or more aspects and/or embodiments disclosed herein in a
simplified form to precede the detailed description presented below.

[0006] According to various aspects, a method for optimizing handover
during voice sessions may comprise detecting a condition triggering a
handover at a wireless device associated with a parent user during a
current voice communication session between the parent user and a target
user, wherein the handover has a type associated with a switching delay,
determining an average mutual silence duration after talk spurts from the
parent user and the target user based on one or more past voice
communication sessions in which at least the parent user participated,
and triggering the handover when a next talk spurt from either the parent
user or the target user ends in response to the determined average mutual
silence duration exceeding the switching delay associated with the
handover type.

[0007] According to various aspects, a wireless device may comprise a
storage device configured to store statistics associated with one or more
past voice communication sessions in which at least a parent user
associated with the wireless device participated and one or more
processors configured to detect a condition triggering a handover during
a current voice communication session between the parent user and a
target user, determine, from the stored statistics, an average mutual
silence duration after talk spurts from the parent user and the target
user based on one or more past voice communication sessions in which at
least the parent user participated, and trigger the handover when a next
talk spurt from either the parent user or the target user ends in
response to the determined average mutual silence duration exceeding a
switching delay associated with a type that corresponds to the triggered
handover.

[0008] According to various aspects, a wireless device may comprise means
for detecting a condition triggering a handover during a current voice
communication session between a parent user associated with the wireless
device and a target user, wherein the handover has a type associated with
a switching delay, means for determining an average mutual silence
duration after talk spurts from the parent user and the target user based
on one or more past voice communication sessions in which at least the
parent user participated, and means for triggering the handover when a
next talk spurt from either the parent user or the target user ends in
response to the determined average mutual silence duration exceeding the
switching delay associated with the handover type.

[0009] According to various aspects, a computer-readable storage medium
may have computer-executable instructions recorded thereon, wherein
executing the computer-executable instructions on a wireless device may
cause the wireless device to detect a condition triggering a handover
during a current voice communication session between a parent user
associated with the wireless device and a target user, wherein the
handover has a type associated with a switching delay, determine an
average mutual silence duration after talk spurts from the parent user
and the target user based on one or more past voice communication
sessions in which at least the parent user participated, and trigger the
handover when a next talk spurt from either the parent user or the target
user ends in response to the determined average mutual silence duration
exceeding the switching delay associated with the handover type.

[0010] Other objects and advantages associated with the aspects and
embodiments disclosed herein will be apparent to those skilled in the art
based on the accompanying drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A more complete appreciation of the various aspects disclosed
herein and many attendant advantages thereof will be readily obtained as
the same becomes better understood through reference to the following
detailed description when considered in connection with the accompanying
drawings, which are presented solely for illustration purposes and not to
limit the disclosure, and in which:

[0012] FIG. 1 illustrates a high-level system architecture of a wireless
communications system, according to one aspect of the disclosure.

[0013] FIG. 2A illustrates an example configuration of a radio access
network (RAN) and a packet-switched portion of a core network for a 1x
EV-DO network, according to one aspect of the disclosure.

[0014] FIG. 2B illustrates an example configuration of the RAN and a
packet-switched portion of a General Packet Radio Service (GPRS) core
network within a 3G UMTS W-CDMA system, according to one aspect of the
disclosure.

[0015] FIG. 2C illustrates another example configuration of the RAN and a
packet-switched portion of a GPRS core network within a 3G UMTS W-CDMA
system, according to one aspect of the disclosure.

[0016] FIG. 2D illustrates an example configuration of the RAN and a
packet-switched portion of the core network that is based on an Evolved
Packet System (EPS) or Long Term Evolution (LTE) network, according to
one aspect of the disclosure.

[0017] FIG. 2E illustrates an example configuration of an enhanced High
Rate Packet Data (HRPD) RAN connected to an EPS or LTE network and also a
packet-switched portion of an HRPD core network, according to one aspect
of the disclosure.

[0018] FIG. 3 illustrates an exemplary wireless communication system that
may enable various wireless telecommunication devices to form a
push-to-talk (PTT) group and communicate with a group communication
server and other computer devices across a wireless network, according to
one aspect of the disclosure.

[0019] FIG. 4 illustrates an exemplary wireless network having a common
cellular configuration in which one or more group communication servers
are configured to control communications among various wireless
telecommunication devices in a PTT group, according to one aspect of the
disclosure.

[0020] FIG. 5 illustrates exemplary wireless telecommunication devices
with computer platforms that can support PTT capabilities, according to
one aspect of the disclosure.

[0021] FIG. 6 illustrates an exemplary signaling call flow in which a
wireless device may initiate a PTT group communication, receive an
initial floor grant, and subsequently release the floor to allow other
PTT group members to take the floor, according to one aspect of the
disclosure.

[0022] FIG. 7 illustrates an exemplary signaling call flow associated with
an intra-LTE handover in an LTE network, according to one aspect of the
disclosure.

[0023] FIG. 8 illustrates an exemplary signaling call flow associated with
an E-UTRAN to UTRAN intra-RAT handover, according to one aspect of the
disclosure.

[0024] FIG. 9 illustrates an exemplary group communication platform that
can control handovers during a PTT session, according to one aspect of
the disclosure.

[0025] FIG. 10 illustrates an exemplary timing diagram in which mutual
silence and/or talk bursts between a parent and target user may provide
statistics to determine a handover trigger point during a PTT session,
according to one aspect of the disclosure.

[0026] FIG. 11 illustrates an exemplary method in which mutual silence
and/or talk burst statistics may be utilized to determine a handover
trigger point during a PTT session, according to one aspect of the
disclosure.

[0027] FIG. 12 illustrates an exemplary signaling call flow in which a
handover during a PTT session may be triggered or delayed based on a talk
burst queue position status, according to one aspect of the disclosure.

[0028] FIG. 13 illustrates an exemplary method in which a handover during
a PTT session may be triggered or delayed based on a talk burst queue
position status, according to one aspect of the disclosure.

[0029] FIG. 14 illustrates an exemplary signaling call flow that may occur
in a PTT session prior to, during, and after a handover, according to one
aspect of the disclosure.

[0030] FIG. 15 illustrates an exemplary base station and an exemplary
wireless communication device that may communicate with one another
during a PTT session, according to one aspect of the disclosure.

[0031] FIG. 16 illustrates an exemplary server (e.g., a group
communication server) that may control communications among various
wireless telecommunication devices in a PTT group, according to one
aspect of the disclosure.

DETAILED DESCRIPTION

[0032] Various aspects are disclosed in the following description and
related drawings. Alternate aspects may be devised without departing from
the scope of the disclosure. Additionally, well-known elements of the
disclosure will not be described in detail or will be omitted so as not
to obscure the relevant details of the disclosure.

[0033] The words "exemplary" and/or "example" are used herein to mean
"serving as an example, instance, or illustration." Any aspect described
herein as "exemplary" and/or "example" is not necessarily to be construed
as preferred or advantageous over other aspects. Likewise, the term
"aspects of the disclosure" does not require that all aspects of the
disclosure include the discussed feature, advantage or mode of operation.
Furthermore, the terms "group communication," "push-to-talk" (or "PTT"),
or other similar variants as used herein are meant to generally refer to
a server arbitrated service between two or more devices.

[0034] The terminology used herein is for the purpose of describing
particular aspects only and is not intended to limit any aspects and/or
embodiments disclosed herein. As used herein, the singular forms "a",
"an" and "the" are intended to include plural forms as well, unless the
context clearly indicates otherwise. It will be further understood that
the terms "comprises," "comprising," "includes," and/or "including," when
used herein, specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the presence
or addition of one or more other features, integers, steps, operations,
elements, components, and/or groups thereof.

[0035] Further, many aspects are described in terms actions to be
performed by, for example, elements of a computing device. It will be
recognized that various actions described herein can be performed by
specific circuits (e.g., an application specific integrated circuit
(ASIC) or another suitable circuit), by program instructions being
executed by one or more processors, or combinations thereof.
Additionally, the actions described herein can be considered to be
embodied entirely within any form of computer readable storage medium
having stored therein a corresponding set of computer instructions that
upon execution would cause an associated processor to perform the
functionality described herein. Thus, the various aspects of the
disclosure may be embodied in a number of different forms, all of which
have been contemplated to be within the scope of the claimed subject
matter. In addition, for each of the aspects described herein, the
corresponding form of any such aspects may be described herein as, for
example, "logic configured to" perform the described action.

[0037] In various embodiments, client devices can communicate with a core
network via the RAN, and through the core network the client devices can
be connected with external networks such as the Internet. Of course,
other mechanisms of connecting to the core network and/or the Internet
are also possible for the client devices, such as over wired access
networks, Wi-Fi networks (e.g., based on IEEE 802.11, etc.) and so on.
Client devices can be embodied by any of a number of types of devices
including but not limited to PC cards, compact flash devices, external or
internal modems, wireless or wireline phones, and so on. A communication
link through which client devices can send signals to the RAN is called
an uplink channel (e.g., a reverse traffic channel, a reverse control
channel, an access channel, etc.). A communication link through which the
RAN can send signals to client devices is called a downlink or forward
link channel (e.g., a paging channel, a control channel, a broadcast
channel, a forward traffic channel, etc.). As used herein the term
traffic channel (TCH) can refer to either an uplink/reverse traffic
channel or a downlink/forward traffic channel.

[0038] The techniques described herein to optimize RAT handover in a PTT
session may be used in various cellular communication systems such as
Code Division Multiple Access (CDMA), Time Division Multiple Access
(TDMA), Frequency Division Multiple Access (FDMA), Orthogonal FDMA
(OFDMA), and Single-Carrier FDMA (SC-FDMA) systems. The terms "system"
and "network" are often used interchangeably. A CDMA system may implement
a radio technology such as Universal Terrestrial Radio Access (UTRA),
CDMA2000, etc. UTRA includes Wideband CDMA (WCDMA) and other variants of
CDMA. CDMA2000covers IS-2000, IS-95 and IS-856 standards. A TDMA system
may implement a RAT such as Global System for Mobile Communications
(GSM). An OFDMA system may implement a RAT such as Evolved UTRA (E-UTRA),
Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),
IEEE 802.20, Flash-OFDM®, etc. UTRA and E-UTRA are part of Universal
Mobile Telecommunication System (UMTS). 3GPP Long Term Evolution (LTE) is
a release of UMTS that uses E-UTRA, which employs OFDMA on the downlink
and SC-FDMA on the uplink UTRA. E-UTRA, UMTS, LTE, and GSM are described
in documents from an organization named "3rd Generation Partnership
Project" (3GPP). CDMA2000 and UMB are described in documents from an
organization named "3rd Generation Partnership Project 2" (3GPP2). For
clarity, certain aspects of the techniques are described below for LTE,
and LTE terminology is used in much of the description below.

[0040] Referring to FIG. 1, UEs 1 . . . N are configured to communicate
with an access network (e.g., the RAN 120, an access point 125, etc.)
over a physical communications interface or layer, shown in FIG. 1 as air
interfaces 104, 106, 108 and/or a direct wired connection. The air
interfaces 104 and 106 can comply with a given cellular communications
protocol (e.g., CDMA, EV-DO, eHRPD, GSM, EDGE, W-CDMA, LTE, etc.), while
the air interface 108 can comply with a wireless IP protocol (e.g., IEEE
802.11). The RAN 120 includes a plurality of access points that serve UEs
over air interfaces, such as the air interfaces 104 and 106. The access
points in the RAN 120 can be referred to as access nodes or ANs, access
points or APs, base stations or BSs, Node Bs, Evolved Node Bs (eNodeBs or
eNBs), and so on. These access points can be terrestrial access points
(or ground stations), or satellite access points. The RAN 120 is
configured to connect to a core network 140 that can perform a variety of
functions, including bridging circuit switched (CS) calls between UEs
served by the RAN 120 and other UEs served by the RAN 120 or a different
RAN altogether, and can also mediate an exchange of packet-switched (PS)
data with external networks such as Internet 175. The Internet 175
includes a number of routing agents and processing agents (not shown in
FIG. 1 for the sake of convenience). In FIG. 1, UE N is shown as
connecting to the Internet 175 directly (i.e., separate from the core
network 140, such as over an Ethernet connection of Wi-Fi or 802.11-based
network). The Internet 175 can thereby function to bridge packet-switched
data communications between UE N and UEs 1 . . . N via the core network
140. Also shown in FIG. 1 is the access point 125 that is separate from
the RAN 120. The access point 125 may be connected to the Internet 175
independent of the core network 140 (e.g., via an optical communication
system such as FiOS, a cable modem, etc.). The air interface 108 may
serve UE 4 or UE 5 over a local wireless connection, such as IEEE 802.11
in an example. UE N is shown as a desktop computer with a wired
connection to the Internet 175, such as a direct connection to a modem or
router, which can correspond to the access point 125 itself in an example
(e.g., a Wi-Fi router with wired and/or wireless connectivity may
correspond to the access point 125).

[0041] Referring to FIG. 1, an application server 170 is shown as
connected to the Internet 175, the core network 140, or both. The
application server 170 can be implemented as a plurality of structurally
separate servers, or alternately may correspond to a single server. As
will be described below in more detail, the application server 170 is
configured to support one or more communication services for UEs that can
connect to the application server 170 via the core network 140 and/or the
Internet 175 (e.g., Voice-over-Internet Protocol (VoIP) sessions,
Voice-over-LTE (VoLTE) sessions, Push-to-Talk (PTT) sessions, group
communication sessions, sessions that involve Rich Communication Services
(RCS) sessions, social networking services, etc.).

[0042] Examples of protocol-specific implementations for the RAN 120 and
the core network 140 are provided below with respect to FIGS. 2A through
2D to help explain the wireless communications system 100 in more detail.
In particular, the components of the RAN 120 and the core network 140
corresponds to components associated with supporting packet-switched (PS)
communications, whereby legacy circuit-switched (CS) components may also
be present in these networks, but any legacy CS-specific components are
not shown explicitly in FIGS. 2A-2D.

[0043] FIG. 2A illustrates an example configuration of the RAN 120 and the
core network 140 for packet-switched communications in a CDMA2000 1x
Evolution-Data Optimized (EV-DO) network according to one aspect of the
disclosure. Referring to FIG. 2A, the RAN 120 includes a plurality of
base stations (BSs) 200A, 205A and 210A that are coupled to a base
station controller (BSC) 215A over a wired backhaul interface. A group of
BSs controlled by a single BSC is collectively referred to as a subnet.
As will be appreciated by one of ordinary skill in the art, the RAN 120
can include multiple BSCs and subnets, and a single BSC is shown in FIG.
2A for the sake of convenience. The BSC 215A communicates with a packet
control function (PCF) 220A within the core network 140 over an A9
connection. The PCF 220A performs certain processing functions for the
BSC 215A related to packet data. The PCF 220A communicates with a Packet
Data Serving Node (PDSN) 225A within the core network 140 over an A11
connection. The PDSN 225A has a variety of functions, including managing
Point-to-Point (PPP) sessions, acting as a home agent (HA) and/or foreign
agent (FA), and is similar in function to a Gateway General Packet Radio
Service (GPRS) Support Node (GGSN) in GSM and UMTS networks (described
below in more detail). The PDSN 225A connects the core network 140 to
external IP networks, such as the Internet 175.

[0044] FIG. 2B illustrates an example configuration of the RAN 120 and a
packet-switched portion of the core network 140 that is configured as a
GPRS core network within a 3G UMTS W-CDMA system according to one aspect
of the disclosure. Referring to FIG. 2B, the RAN 120 includes a plurality
of Node Bs 200B, 205B and 210B that are coupled to a Radio Network
Controller (RNC) 215B over a wired backhaul interface. Similar to 1x
EV-DO networks, a group of Node Bs controlled by a single RNC is
collectively referred to as a subnet. As will be appreciated by one of
ordinary skill in the art, the RAN 120 can include multiple RNCs and
subnets, and a single RNC is shown in FIG. 2B for the sake of
convenience. The RNC 215B is responsible for signaling, establishing and
tearing down bearer channels (i.e., data channels) between a Serving GRPS
Support Node (SGSN) 220B in the core network 140 and UEs served by the
RAN 120. If link layer encryption is enabled, the RNC 215B also encrypts
the content before forwarding it to the RAN 120 for transmission over an
air interface. The function of the RNC 215B is well-known in the art and
will not be discussed further for the sake of brevity.

[0045] In FIG. 2B, the core network 140 includes the above-noted SGSN 220B
(and potentially a number of other SGSNs as well) and a GGSN 225B.
Generally, GPRS is a protocol used in GSM for routing IP packets. The
GPRS core network (e.g., the GGSN 225B and one or more SGSNs 220B) is the
centralized part of the GPRS system and also provides support for W-CDMA
based 3G access networks. The GPRS core network is an integrated part of
the GSM core network (i.e., the core network 140) that provides mobility
management, session management, and transport for IP packet services in
GSM and W-CDMA networks.

[0046] The GPRS Tunneling Protocol (GTP) is the defining IP protocol of
the GPRS core network. The GTP is the protocol which allows end users
(e.g., UEs) of a GSM or W-CDMA network to move from place to place while
continuing to connect to the Internet 175 as if from one location at the
GGSN 225B. This is achieved by transferring the respective UE's data from
the UE's current SGSN 220B to the GGSN 225B, which is handling the
respective UE's session.

[0047] Three forms of GTP are used by the GPRS core network; namely, (i)
GTP-U, (ii) GTP-C and (iii) GTP' (GTP Prime). GTP-U is used for transfer
of user data in separated tunnels for each packet data protocol (PDP)
context. GTP-C is used for control signaling (e.g., setup and deletion of
PDP contexts, verification of GSN reachability, updates or modifications
such as when a subscriber moves from one SGSN to another, etc.). GTP' is
used for transfer of charging data from GSNs to a charging function.

[0048] Referring to FIG. 2B, the GGSN 225B acts as an interface between a
GPRS backbone network (not shown) and the Internet 175. The GGSN 225B
extracts packet data with associated a packet data protocol (PDP) format
(e.g., IP or PPP) from GPRS packets coming from the SGSN 220B, and sends
the packets out on a corresponding packet data network. In the other
direction, the incoming data packets are directed by the GGSN connected
UE to the SGSN 220B which manages and controls the Radio Access Bearer
(RAB) of a target UE served by the RAN 120. Thereby, the GGSN 225B stores
the current SGSN address of the target UE and its associated profile in a
location register (e.g., within a PDP context). The GGSN 225B is
responsible for IP address assignment and is the default router for a
connected UE. The GGSN 225B also performs authentication and charging
functions.

[0049] The SGSN 220B is representative of one of many SGSNs within the
core network 140, in an example. Each SGSN is responsible for the
delivery of data packets from and to the UEs within an associated
geographical service area. The tasks of the SGSN 220B includes packet
routing and transfer, mobility management (e.g., attach/detach and
location management), logical link management, and authentication and
charging functions. The location register of the SGSN 220B stores
location information (e.g., current cell, current VLR) and user profiles
(e.g., IMSI, PDP address(es) used in the packet data network) of all GPRS
users registered with the SGSN 220B, for example, within one or more PDP
contexts for each user or UE. Thus, SGSNs 220B are responsible for (i)
de-tunneling downlink GTP packets from the GGSN 225B, (ii) uplink tunnel
IP packets toward the GGSN 225B, (iii) carrying out mobility management
as UEs move between SGSN service areas and (iv) billing mobile
subscribers. As will be appreciated by one of ordinary skill in the art,
aside from (i)-(iv), SGSNs configured for GSM/EDGE networks have slightly
different functionality as compared to SGSNs configured for W-CDMA
networks.

[0050] The RAN 120 (e.g., or UTRAN, in UMTS system architecture)
communicates with the SGSN 220B via a Radio Access Network Application
Part (RANAP) protocol. RANAP operates over an Iu interface (Iu-ps), with
a transmission protocol such as Frame Relay or IP. The SGSN 220B
communicates with the GGSN 225B via a Gn interface, which is an IP-based
interface between SGSN 220B and other SGSNs (not shown) and internal
GGSNs (not shown), and uses the GTP protocol defined above (e.g., GTP-U,
GTP-C, GTP', etc.). In the embodiment of FIG. 2B, the Gn between the SGSN
220B and the GGSN 225B carries both the GTP-C and the GTP-U. While not
shown in FIG. 2B, the Gn interface is also used by the Domain Name System
(DNS). The GGSN 225B is connected to a Public Data Network (PDN) (not
shown), and in turn to the Internet 175, via a Gi interface with IP
protocols either directly or through a Wireless Application Protocol
(WAP) gateway.

[0051] FIG. 2C illustrates another example configuration of the RAN 120
and a packet-switched portion of the core network 140 that is configured
as a GPRS core network within a 3G UMTS W-CDMA system according to one
aspect of the disclosure. Similar to FIG. 2B, the core network 140
includes the SGSN 220B and the GGSN 225B. However, in FIG. 2C, Direct
Tunnel is an optional function in Iu mode that allows the SGSN 220B to
establish a direct user plane tunnel, GTP-U, between the RAN 120 and the
GGSN 225B within a PS domain. A Direct Tunnel capable SGSN, such as SGSN
220B in FIG. 2C, can be configured on a per GGSN and per RNC basis
whether or not the SGSN 220B can use a direct user plane connection. The
SGSN 220B in FIG. 2C handles the control plane signaling and makes the
decision of when to establish Direct Tunnel. When the RAB assigned for a
PDP context is released (i.e. the PDP context is preserved) the GTP-U
tunnel is established between the GGSN 225B and SGSN 220B in order to be
able to handle the downlink packets.

[0052] FIG. 2D illustrates an example configuration of the RAN 120 and a
packet-switched portion of the core network 140 based on an Evolved
Packet System (EPS) or LTE network, according to one aspect of the
disclosure. Referring to FIG. 2D, unlike the RAN 120 shown in FIGS.
2B-2C, the RAN 120 in the EPS/LTE network is configured with a plurality
of eNodeBs 200D, 205D and 210D, without the RNC 215B from FIGS. 2B-2C.
This is because eNodeBs in EPS/LTE networks do not require a separate
controller (i.e., the RNC 215B) within the RAN 120 to communicate with
the core network 140. In other words, some of the functionality of the
RNC 215B from FIGS. 2B-2C is built into each respective eNodeB of the RAN
120 in FIG. 2D.

[0053] In FIG. 2D, the core network 140 includes a plurality of Mobility
Management Entities (MMEs) 215D and 220D, a Home Subscriber Server (HSS)
225D, a Serving Gateway (S-GW) 230D, a Packet Data Network Gateway (P-GW)
235D and a Policy and Charging Rules Function (PCRF) 240D. Network
interfaces between these components, the RAN 120, and the Internet 175
are illustrated in FIG. 2D and further explained below in Table 1.

TABLE-US-00001
TABLE 1
EPS/LTE Core Network Connection Definitions
Network Interface Description
S1-MME Reference point for the control plane protocol between RAN 120 and
MME 215D.
S1U Reference point between RAN 120 and S-GW 230D for the per bearer
user plane tunneling and inter-eNodeB path switching during handover.
S5 Provides user plane tunneling and tunnel management between S-GW
230D and P-GW 235D. It is used for S-GW relocation due to UE
mobility and if the S-GW 230D needs to connect to a non-collocated P-
GW for the required PDN connectivity.
S6a Enables transfer of subscription and authentication data for
authenticating/authorizing user access to the evolved system
(Authentication, Authorization, and Accounting [AAA] interface)
between MME 215D and HSS 225D.
Gx Provides transfer of Quality of Service (QoS) policy and charging rules
from PCRF 240D to Policy a Charging Enforcement Function (PCEF)
component (not shown) in the P-GW 235D.
S8 Inter-PLMN reference point providing user and control plane between
the S-GW 230D in a Visited Public Land Mobile Network (VPLMN)
and the P-GW 235D in a Home Public Land Mobile Network
(HPLMN). S8 is the inter-PLMN variant of S5.
S10 Reference point between MMEs 215D and 220D for MME relocation
and MME to MME information transfer.
S11 Reference point between MME 215D and S-GW 230D.
SGi Reference point between the P-GW 235D and the packet data network,
shown in FIG. 2D as the Internet 175. The Packet data network may be
an operator external public or private packet data network or an intra-
operator packet data network (e.g., for provision of IMS services). This
reference point corresponds to Gi for 3GPP accesses.
X2 Reference point between two different eNodeBs used for UE handoffs.
Rx Reference point between the PCRF 240D and an application function
(AF) that is used to exchanged application-level session information,
where the AF is represented in FIG. 1 by the application server 170.

[0054] A high-level description of the components shown in the RAN 120 and
core network 140 of FIG. 2D will now be described. However, these
components are each well-known in the art from various 3GPP TS standards,
and the description contained herein is not intended to be an exhaustive
description of all functionalities performed by these components.

[0056] Referring to FIG. 2D, the S-GW 230D is the gateway that terminates
the interface toward the RAN 120. For each UE associated with the core
network 140 for an EPS-based system, at a given point of time, there is a
single S-GW. The functions of the S-GW 230D, for both the GTP-based and
the Proxy Mobile IPv6 (PMIP)-based S5/S8, include: Mobility anchor point,
Packet routing and forwarding, and setting the DiffServ Code Point (DSCP)
based on a QoS Class Identifier (QCI) of the associated EPS bearer.

[0057] Referring to FIG. 2D, the P-GW 235D is the gateway that terminates
the SGi interface toward the Packet Data Network (PDN), e.g., the
Internet 175. If a UE is accessing multiple PDNs, there may be more than
one P-GW for that UE; however, a mix of S5/S8 connectivity and Gn/Gp
connectivity is not typically supported for that UE simultaneously. P-GW
functions include for both the GTP-based S5/S8: Packet filtering (by deep
packet inspection), UE IP address allocation, setting the DSCP based on
the QCI of the associated EPS bearer, accounting for inter operator
charging, uplink (UL) and downlink (DL) bearer binding as defined in 3GPP
TS 23.203, UL bearer binding verification as defined in 3GPP TS 23.203.
The P-GW 235D provides PDN connectivity to both GSM/EDGE Radio Access
Network (GERAN)/UTRAN only UEs and E-UTRAN-capable UEs using any of
E-UTRAN, GERAN, or UTRAN. The P-GW 235D provides PDN connectivity to
E-UTRAN capable UEs using E-UTRAN only over the S5/S8 interface.

[0058] Referring to FIG. 2D, the PCRF 240D is the policy and charging
control element of the EPS-based core network 140. In a non-roaming
scenario, there is a single PCRF in the HPLMN associated with a UE's
Internet Protocol Connectivity Access Network (IP-CAN) session. The PCRF
terminates the Rx interface and the Gx interface. In a roaming scenario
with local breakout of traffic, there may be two PCRFs associated with a
UE's IP-CAN session: A Home PCRF (H-PCRF) is a PCRF that resides within a
HPLMN, and a Visited PCRF (V-PCRF) is a PCRF that resides within a
visited VPLMN. PCRF is described in more detail in 3GPP TS 23.203, and as
such will not be described further for the sake of brevity. In FIG. 2D,
the application server 170 (e.g., which can be referred to as the AF in
3GPP terminology) is shown as connected to the core network 140 via the
Internet 175, or alternatively to the PCRF 240D directly via an Rx
interface. Generally, the application server 170 (or AF) is an element
offering applications that use IP bearer resources with the core network
(e.g. UMTS PS domain/GPRS domain resources/LTE PS data services). One
example of an application function is the Proxy-Call Session Control
Function (P-CSCF) of the IP Multimedia Subsystem (IMS) Core Network
subsystem. The AF uses the Rx reference point to provide session
information to the PCRF 240D. Any other application server offering IP
data services over cellular network can also be connected to the PCRF
240D via the Rx reference point.

[0059] FIG. 2E illustrates an example of the RAN 120 configured as an
enhanced High Rate Packet Data (HRPD) RAN connected to an EPS or LTE
network 140A and also a packet-switched portion of an HRPD core network
140B according to one aspect of the disclosure. The core network 140A is
an EPS or LTE core network, similar to the core network described above
with respect to FIG. 2D.

[0060] In FIG. 2E, the eHRPD RAN includes a plurality of base transceiver
stations (BTSs) 200E, 205E and 210E, which are connected to an enhanced
BSC (eBSC) and enhanced PCF (ePCF) 215E. The eBSC/ePCF 215E can connect
to one of the MMEs 215D or 220D within the EPS core network 140A over an
S101 interface, and to an HRPD serving gateway (HSGW) 220E over A10
and/or A11 interfaces for interfacing with other entities in the EPS core
network 140A (e.g., the S-GW 220D over an S103 interface, the P-GW 235D
over an S2a interface, the PCRF 240D over a Gxa interface, a 3GPP AAA
server (not shown explicitly in FIG. 2D) over an STa interface, etc.).
The HSGW 220E is defined in 3GPP2 to provide the interworking between
HRPD networks and EPS/LTE networks. As will be appreciated, the eHRPD RAN
and the HSGW 220E are configured with interface functionality to EPC/LTE
networks that is not available in legacy HRPD networks.

[0061] Turning back to the eHRPD RAN, in addition to interfacing with the
EPS/LTE network 140A, the eHRPD RAN can also interface with legacy HRPD
networks such as HRPD network 140B. As will be appreciated the HRPD
network 140B is an example implementation of a legacy HRPD network, such
as the EV-DO network from FIG. 2A. For example, the eBSC/ePCF 215E can
interface with an authentication, authorization and accounting (AAA)
server 225E via an A12 interface, or to a PDSN/FA 230E via an A10 or A11
interface. The PDSN/FA 230E in turn connects to HA 235A, through which
the Internet 175 can be accessed. In FIG. 2E, certain interfaces (e.g.,
A13, A16, H1, H2, etc.) are not described explicitly but are shown for
completeness and would be understood by one of ordinary skill in the art
familiar with HRPD or eHRPD.

[0062] Referring to FIGS. 2B-2E, it will be appreciated that LTE core
networks (e.g., FIG. 2D) and HRPD core networks that interface with eHRPD
RANs and HSGWs (e.g., FIG. 2E) can support network-initiated Quality of
Service (QoS) (e.g., by the P-GW, GGSN, SGSN, etc.) in certain cases.

[0063] According to various embodiments, FIG. 3 illustrates an exemplary
wireless communication system 300 in which a push-to-talk (PTT)
communication group 312 may include various wireless telecommunication
devices, such as a wireless telephone 314, a smart pager 316, and a
personal digital assistant (PDA) 318, wherein the various wireless
telecommunication devices 314, 316, 318 in the PTT communication group
312 may communicate with a group communication server 332 and other
computer devices across a wireless network 320. In the system 300 shown
therein, each wireless telecommunication device 314, 316, 318, etc. in
the PTT communication group 312 can selectively and directly communicate
across the wireless communication network 320 with a target set that
includes one or more other wireless telecommunication devices in the PTT
communication group 312. For example, in various embodiments, the target
set associated with the mobile telephone 314 can be all devices in the
PTT communication group 312 or a subset thereof, such as pager 316 and
PDA 318.

[0064] In various embodiments, a wireless telecommunication device in the
PTT communication group 312 (e.g., mobile telephone 314) may send a flag
to at least the group communication server 332, which may reside on a
server-side local area network (LAN) 330 across the wireless network 320,
to indicate that the wireless device is present or otherwise accessible
on the wireless network 320. The group communication server 332 can then
share the presence information with the target set associated with the
wireless telecommunication device and/or share the presence information
associated with the wireless telecommunication device with other computer
devices that reside on the server-side LAN 330 or are otherwise
accessible via the wireless network 320. The group communication server
332 can have an attached or accessible database 334 to store group
identification data associated with the wireless telecommunication
devices in the PTT communication group 312. Furthermore, in various
embodiments, a data store 336, shown in FIG. 3 as a file management
server, may be present on the server-side LAN 330. However, those skilled
in the art will appreciate that the computer components resident on the
server-side LAN 330, accessible via the wireless network 320, within the
PTT communication group 312, or the Internet generally, are not limited
to the exemplary components shown in FIG. 3.

[0065] In various embodiments, direct communication (e.g., a PTT
communication) can be established through half-duplex channels between
one or more communicating wireless telecommunication devices 314, 316,
318, etc. and/or one or more additional wireless telecommunication
devices in the target set associated therewith. Furthermore, the group
communication server 332 can attempt to bridge the requested direct
communication with the target set if at least one wireless
telecommunication device in the target set has informed the group
communication server 332 that the at least one wireless telecommunication
device is present or otherwise accessible on the wireless network 320.
Alternatively (or additionally), the group communication server 332 can
inform the wireless telecommunication device 314, 316, 318, etc. that a
direct communication to the target set could not be bridged if no
wireless telecommunication device (or at least one wireless
telecommunication device) in the target set has not indicated presence on
the wireless network 320 to the group communication server 332. Further,
while FIG. 3 shows the group communication server 332 as having the
attached database 334 with group identification data, in various
embodiments the group communication server 332 can have the group
identification data resident thereupon and perform all storage functions
described herein locally.

[0066] In overview, the system 300 shown in FIG. 3 may include at least
one wireless telecommunication device (e.g., mobile telephone 314) that
is a member in the PTT communication group 312 that communicate with each
other in direct group communications across the wireless communication
network 320, wherein the at least one wireless telecommunication device
may selectively send group-directed media to other members of the PTT
communication group 312 and at least one group communication server 332
may store information about one or more PTT communication groups 312 on
the wireless communication network 320, including the information about
the identities associated with specific member wireless telecommunication
devices in the PTT communication groups 312. The group communication
server 32 may further selectively receive group-directed media from
sending wireless telecommunication devices (e.g., mobile telephone 314)
in the PTT communication group 312 and send the received group-directed
media to the other member wireless telecommunication devices in the PTT
communication group 312.

[0067] Additionally, in various embodiments, the system 300 can further
include a data store 336 in communication with the group communication
server 332, which may be configured to send group-directed media to the
data store 336. The data store 336 may thereby receive the group-directed
media from the wireless telecommunication device (e.g., mobile phone 314)
and selectively permit members in the PTT communication group 312 to
access the group-directed media stored therein across the wireless
communication network 320. Furthermore, the group-directed media can be
any suitable media type, which may include, without limitation, graphic
media or pictures (e.g., in JPEG, TIF, and other formats), audio files
(e.g., in MP3, MP4, WAV, and other formats, etc.), streaming media (e.g.,
PowerPoint files, MOV files, and other multimedia application files), and
other application-specific data or custom application data, which may
either reside at the wireless telecommunication device 314, 316, 318,
etc. or in communication therewith. The group-directed media can also be
an interactive session on another computer device on the wireless
communication network 320 (e.g., a game hosted on data store 336 or a
private bulletin board), half-duplex video conferencing among members in
the PTT communication group 312 (e.g., where a picture corresponding to
the speaker may be broadcast to the other group members in substantially
real-time or according to a suitable delay), location information (e.g.,
GPS coordinates or network locations), or other suitable media types.

[0068] In various embodiments, one or more wireless telecommunication
device 314, 316, 318, etc. in the PTT communication group 312 may further
implement a floor control mechanism that may cause the one or more
wireless telecommunication device 314, 316, 318, etc. to trigger a floor
request, stream audio data during a period when the floor has been
granted to the one or more wireless telecommunication device 314, 316,
318, etc., and subsequently release the floor to allow other members in
the PTT communication group 312 to take the floor. Furthermore, in
various embodiments, one or more wireless telecommunication device 314,
316, 318, etc. in the PTT communication group 312 may implement a
handover control module that may monitor behavior during half-duplex
(e.g., push-to-talk) and/or full-duplex Voice-over-Internet Protocol
(VoIP) sessions with various target users and store various statistics
that can be utilized to control whether and/or when to trigger a handover
during subsequent VoIP sessions. For example, the statistics that the
handover control module maintains may indicate an average number of times
that the "parent" user (i.e., the user who owns or is otherwise
associated with the wireless telecommunication device implementing the
handover control module) took the floor during one or more VoIP sessions
with each individual target user, an average number of times that each
target user took the floor during the one or more VoIP sessions with the
parent user, an average mutual silence duration between the parent user
and each target user during the one or more VoIP sessions, and handover
statistics that indicate average delays that occurred in relation to
intra-RAT and inter-RAT handovers. Accordingly, as will be described in
further detail below, the statistics that the handover control module
maintains may be utilized to determine whether and/or when to trigger a
handover during half-duplex and/or full-duplex VoIP sessions based on
past user behavior and the particular handover type.

[0069] According to various embodiments, FIG. 4 illustrates an exemplary
wireless network having a common cellular configuration in which one or
more group communication servers 432 are configured to control
communications among various wireless telecommunication devices in a PTT
group, which include wireless telecommunication devices 470, 472, 474,
476, etc. in the example illustrated in FIG. 4. Furthermore, those
skilled in the art will appreciate that the wireless network shown in
FIG. 4 is merely exemplary and can include any system in which various
remote modules can communicate over-the-air between and among each other
and/or between and among components in a wireless network, which may
include, without limitation, wireless network carriers and/or servers. In
various embodiments, the one or more group communication servers 432 may
be connected to a server-side LAN 450 and wireless telecommunication
devices 470, 472, 474, 476, etc. can request packet data sessions from
the group communication servers 432 using suitable data service options.

[0070] In various embodiments, the one or more group communication servers
432 may be connected to a wireless service provider packet data service
node (PDSN) 452 that may reside on a carrier network 454, wherein each
PSDN 452 can interface with a base station controller (BSC) 464 at a base
station 460 through a packet control function (PCF) 462, which may
typically be located in the base station 460. The carrier network 454 may
control messages, which generally comprise data packets, sent to a
messaging service controller (MSC) 458 and communicate with the MSC 458
over a network, the Internet, and/or a plain ordinary telephone system
(POTS). In various embodiments, the network or Internet connection
between the carrier network 454 and the MSC 458 may typically transfer
data, while the POTS may typically transfer voice information.
Furthermore, in various embodiments, the MSC 458 can be connected to one
or more base stations 460, and in a similar manner to the carrier network
454, the MSC 458 may typically be connected to a branch-to-source (BTS)
466 through the network and/or the Internet to support data transfer and
through POTS to support transferring voice information. In various
embodiments, the BTS 466 may ultimately broadcast and receive messages
wirelessly to and from the wireless telecommunication devices 470, 472,
474, 476, etc. using short messaging service (SMS) or other suitable
over-the-air methods. Those skilled in the art will further appreciate
that carrier boundaries and/or PTT operator network boundaries do not
inhibit or prohibit sharing data in the manner described herein.

[0071] In general, cellular telephones and mobile telecommunication
devices (e.g., wireless telecommunication devices 470, 472, 474, 476,
etc.) are being manufactured with increased computing capabilities and
are becoming tantamount to personal computers and hand-held PDAs. These
"smart" cellular telephones allow software developers to create software
applications that can be downloaded and executed on a processor
associated with the wireless telecommunication devices 470, 472, 474,
476, etc. (e.g., web pages, applets, MIDlets, games, data, etc.).
Furthermore, in wireless telecommunication devices that have designated a
PTT communication group (e.g., PTT communication group 312 as shown in
FIG. 3), the wireless communication devices can directly connect with
other members in the PTT communication group to engage in voice and data
communication. However, all such direct communications will occur
typically through, or under the control of, the one or more group
communication servers 432. Although all data packets communicated among
the wireless telecommunication devices 470, 472, 474, 476, etc. do not
necessarily have to travel through the one or more group communication
servers 432, the one or more group communication servers 432 may
generally provide ultimate control over the communicated data packets
because the group communication servers 432 are typically the only
components on the server-side LAN 450 that may know and/or retrieve the
identities associated with the members in the PTT communication group, or
direct the identities associated with the members in the PTT
communication group to other computer devices.

[0072] According to various embodiments, FIG. 5 illustrates exemplary
wireless telecommunication devices that may have computer platforms that
can supports PTT capabilities. In particular, FIG. 5, wireless
telecommunication device 500A is illustrated as a calling telephone and
wireless telecommunication device 500B is illustrated as a touchscreen
device (e.g., a smart phone, a tablet computer, etc.). As shown in FIG.
5, an external casing of wireless telecommunication device 500A is
configured with an antenna 505A, display 510A, at least one button 515A
(e.g., a PTT button, a power button, a volume control button, etc.) and a
keypad 520A among other components, as is known in the art. Also, an
external casing of wireless telecommunication device 500B is configured
with a touchscreen display 505B, peripheral buttons 510B, 515B, 520B and
525B (e.g., a power control button, a volume or vibrate control button,
an airplane mode toggle button, etc.), at least one front-panel button
530B (e.g., a Home button, etc.), among other components, as is known in
the art. In various embodiments, the PTT button 515A and/or other
peripheral buttons 510B, 515B, 520B and 525B may be used to open direct
communication to a target set that includes one or more member devices in
a communication group. However, those skilled in the art will appreciate
that other devices and methods can be alternately used to engage in a PTT
communication, such as a "soft key" on touch screen display 505B, other
methods as known in the art, and/or or the voice-activated floor control
mechanisms that will be described in further detail below. Furthermore,
in addition to presenting information about ongoing group communications
and/or PTT communications, the display 510A and/or 505B can present
information that can be used to control or otherwise configure the
voice-activated floor control mechanisms described more fully below.

[0073] In various embodiments, while not shown explicitly as part of
wireless telecommunication device 500B, the wireless telecommunication
device 500B can include one or more external antennas and/or one or more
integrated antennas that are built into the external casing of wireless
telecommunication device 500B, including but not limited to Wi-Fi
antennas, cellular antennas, satellite position system (SPS) antennas
(e.g., global positioning system (GPS) antennas), and so on, and the
wireless telecommunication device 500A may likewise include one or more
external and/or integrated antennas in addition to the antenna 505A. In
any case, the one or more external and/or integrated antennas (including
at least the antenna 505A) can be used to open a direct communication
channel with the wireless telecommunication devices 500A and/or 500B and
thereby provide a direct communication interface to the wireless
telecommunication devices 500A and/or 500B, wherein the direct
communication interface may typically comprise hardware known to those
skilled in the art. Furthermore, in various embodiments, the direct
communication interface can integrate with standard communication
interfaces associated with wireless telecommunication devices 500A and/or
500B that are ordinarily used to carry voice and data transmitted to and
from the wireless telecommunication devices 500A and/or 500B.

[0074] Furthermore, although internal components of wireless
telecommunication device 500A and wireless telecommunication device 500B
can be embodied with different hardware configurations, FIG. 5 shows a
platform 502 that may provide a basic high-level configuration for
internal hardware components associated with wireless telecommunication
devices 500A and/or 500B. In particular, the platform 502 can generally
receive and execute software applications, data and/or commands
transmitted from a cellular network that may ultimately come from the
core network, the Internet, and/or other remote servers and networks
(e.g., an application server, web URLs, etc.). The platform 502 can also
independently execute locally stored applications without cellular
network interaction. The platform 502 can include a transceiver 506
coupled to an application specific integrated circuit (ASIC) 508, or
other processor, microprocessor, logic circuit, or other data processing
device, wherein the transceiver 506 may comprise a receiver that can
receive a signal from, for instance, a receive antenna (e.g., the antenna
505A associated with wireless telecommunication device 500A, one or more
external and/or integrated antennas associated with wireless
telecommunication devices 500A and/or 500B, etc.), perform typical
actions on the received signal (e.g., filtering, amplifying,
downconverting, etc.), digitize the conditioned signal to obtain samples,
and demodulate received symbols that are then provided to the ASIC 508 or
other processor for channel estimation. Furthermore, the transceiver 506
may comprise a transmitter that can transmit a signal using a transmit
antenna (e.g., the antenna 505A associated with wireless
telecommunication device 500A, one or more external and/or integrated
antennas associated with wireless telecommunication devices 500A and/or
500B, etc.).

[0075] In various embodiments, the ASIC 508 or other processor coupled to
the transceiver 506 may execute the application programming interface
(API) 512 layer that interfaces with any application environment resident
in the memory 514, which can include the operating system loaded on the
ASIC 508 and/or any other resident programs in the memory 514 (e.g., the
"binary runtime environment for wireless" (BREW) wireless device software
platform developed by QUALCOMM®). The memory 514 can be comprised of
read-only memory (ROM) or random-access memory (RAM), electrically
erasable programmable ROM (EEPROM), flash cards, or any memory common to
computer platforms. The platform 502 also can include a local database
516 that can store applications not actively used in memory 514, as well
as other data. The local database 516 is typically a flash memory cell,
but can be any secondary storage device as known in the art, such as
magnetic media, EEPROM, optical media, tape, soft or hard disk, or the
like.

[0076] Accordingly, an aspect of the disclosure can include wireless
telecommunication devices 500A, 500B, etc. that have the ability to
perform the functions described herein. As will be appreciated by those
skilled in the art, the various logic elements can be embodied in
discrete elements, software modules executed on a processor or any
combination of software and hardware to achieve the functionality
disclosed herein. For example, ASIC 508, memory 514, API 512 and local
database 516 may all be used cooperatively to load, store and execute the
various functions disclosed herein and thus the logic to perform these
functions may be distributed over various elements. Alternatively, the
functionality could be incorporated into one discrete component.
Furthermore, certain wireless telecommunication devices that may be used
in the various embodiments disclosed herein may not include certain
components and/or functionalities associated with the wireless
telecommunication devices 500A and 500B shown in FIG. 5. For example,
certain wireless devices may support PTT communication despite not having
a PTT button 515A or other peripheral buttons 510B, 515B, 520B and 525B
that can provide a function corresponding to a PTT button 515A (e.g., a
smartwatch running a PTT client), whereby wireless devices that support
PTT communication despite not having a PTT button 515A or other physical
mechanism that can provide a function corresponding thereto may
nonetheless achieve substantially the same functionality using the
voice-activated floor control mechanisms that will be described in
further detail below. However, those skilled in the art will appreciate
that the wireless telecommunication devices 500A and 500B shown in FIG. 5
that do have a PTT button 515A or other peripheral buttons 510B, 515B,
520B and 525B that can provide a function corresponding thereto may
likewise use and obtain the benefits from the voice-activated floor
control mechanisms that will be described in further detail below (e.g.,
to trigger floor requests, floor releases, and other floor-related
functions in a hands-free environment). Therefore, those skilled in the
art will appreciate that the features associated with the wireless
telecommunication devices 500A and 500B shown in FIG. 5 are merely
illustrative and the disclosure is not limited to the illustrated
features or arrangements.

[0077] The wireless communication between the wireless telecommunication
devices 500A and/or 500B can be based on different technologies, such as
CDMA, W-CDMA, time division multiple access (TDMA), frequency division
multiple access (FDMA), Orthogonal Frequency Division Multiplexing
(OFDM), GSM, or other protocols that may be used in a wireless
communications network or a data communications network. As discussed in
the foregoing and known in the art, voice transmission and/or data can be
transmitted to the wireless telecommunication devices 500A and/or 500B
from and using various networks and network configurations. Accordingly,
the illustrations provided herein are not intended to limit the aspects
of the disclosure and are merely to aid in the description of various
aspects disclosed herein.

[0078] According to various embodiments, FIG. 6 illustrates an exemplary
signaling call flow in which an originating wireless device (or
originating PTT client) 610 may initiate a PTT group communication,
receive an initial floor grant, and subsequently release the floor to
allow other PTT group members to take the floor. In particular, in
response to the originating PTT client 610 requesting a direct PTT call
with at least one target wireless device (or target PTT client) 630, the
originating PTT client 610 may transmit a call setup request to a
Dispatch Call Handler (DCH) 620. For example, in various embodiments, the
call setup request may include an address associated with the target PTT
client 630, an application identifier associated with the target PTT
client 630, and/or other suitable information associated with the target
PTT client 630 that may be communicated to the DCH 620 to initiate a PTT
group call. The DCH 620 may then perform the PTT call setup functions,
which may include locating the target PTT client 630, applying any
appropriate call restrictions, selecting a vocoder, and assigning a Media
Control Unit (MCU) 625 resource. In addition, the DCH 620 may check
capabilities associated with the target PTT client 630 to verify that the
target PTT client 630 can support the requested PTT communication. In
response to suitably verifying that the target PTT client 630 can support
the requested PTT communication, the DCH 620 may then send a message
announcing the call to the target PTT client 630, which may transmit a
message accepting the PTT call to the DCH 620 in response to determining
that PTT communications are available on the target PTT client 630.

[0079] In various embodiments, in response to receiving the
acknowledgement accepting the call from the target PTT client 630, the
DCH 620 may transmit a floor grant message to the originating PTT client
610, which may indicate that the PTT call is being established and the
originating PTT client 610 can start collecting media (e.g., voice data
or other appropriate media). As such, the originating PTT client 610 may
notify the user that the floor was granted and that the user can
therefore start to speak, wherein the originating PTT client 610 may
collect and buffer voice media (i.e., the talk spurt collected from the
user via the vocoder). In response to the originating PTT client 610
receiving and acknowledging a contact information message from the MCU
625, the buffered voice media (or group traffic) may be sent to the MCU
625, which may likewise buffer the voice media and forward the group
traffic to the target PTT client 630 after receiving an acknowledgement
to the contact information message from the target PTT client 630. At
some subsequent point in time, the originating PTT client 610 may release
the initial floor grant and transmit a PTT release message to the MCU
625, which may then release the floor and send a message acknowledging
the floor release to the originating PTT client 610. Accordingly, the
originating PTT client 610, the target PTT client 630, and/or any other
PTT clients that may be participating in the PTT call may then take the
floor in a substantially similar manner.

[0080] In various embodiments, during a PTT call, a full-duplex call, or
other real-time multimedia session in which a wireless device
communicates over a wireless access network, certain conditions may
trigger a handover to switch the wireless device from a current base
station to a target base station and/or from a current access network to
a different access network. For example, user mobility may trigger a
handover where the wireless device approaches the edge of the coverage
area associated with a current base station or access network, radio
conditions may trigger a handover where the wireless device receives
stronger signals from a neighbor base station or access network than a
current base station or access network, cell capacity may trigger a
handover where a neighbor base station or access network has less loading
than the current base station or access network, and so on. However,
depending on the target base station and/or the target access network,
the voice call or other real-time multimedia session may end if the
handover delay results in inactivity leading to a dropped call,
perceivable "clicks" may occur due to packet loss and/or delays during
the handover, whereby handovers that are triggered while a wireless
device is involved in a voice call or other real-time multimedia session
may cause session interruption, packet delay, packet loss, and degraded
user experience, among other problems.

[0081] For example, according to various embodiments, FIG. 7 illustrates
an exemplary signaling call flow associated with an intra-LTE handover in
an LTE network, which may generally correspond to a handover where a
wireless device (or UE) 710 detaches from a source eNB 720 and
synchronizes to a target eNB 730 using an X2 interface that provides a
reference point between the source eNB 720 and the target eNB 730 used
for UE handovers. In particular, at 742, the UE 710 may transmit a
measurement report to the source eNB 720, wherein the measurement report
may indicate a strength at which a signal was received from the source
eNB 720, a strength at which a signal was received from the target eNB
730, or any other suitable measurement information that the UE 710 may be
configured to report to the source eNB 720. In the illustrated example,
the source eNB 720 may determine that conditions warrant triggering a
handover to the target eNB 730 based on the measurement report received
from the UE 710. As such, the UE 710 may receive a Radio Link Control
(RLC) Protocol Data Unit (PDU) from the source eNB 720 at 744 and the UE
710 may further receive a Radio Resource Control (RRC) connection
reconfiguration message from the source eNB 720 at 746, wherein the RLC
PDU received at 744 may represent the last data packet that the UE 710
receives from the source eNB 720 and the RRC connection reconfiguration
message includes information associated with the target eNB 730.

[0082] In various embodiments, the UE 710 may then detach from the source
eNB 710 and perform either a contention-free or contention-based Random
Access Channel (RACH) procedure to synchronize to the target eNB 730 at
748. Accordingly, after the UE 710 successfully synchronizes to the
target eNB 730, at 750 the UE 710 may transmit an RRC connection
reconfiguration complete message to the target eNB 730. In that context,
a duration between the time when the UE 710 received the RRC connection
reconfiguration message from the source eNB 720 to the time when the UE
710 transmitted the RRC connection reconfiguration complete message to
the target eNB 730 may represent a total control plane (C-Plane) handover
time 762. In various embodiments, after transmitting the RRC connection
reconfiguration complete message to the target eNB 730, the UE 710 may
then collect system information from the target eNB at 752 and receive a
first RLC PDU from the target eNB 730 at 754, wherein the first RLC PDU
received at 754 may represent the first data packet that the UE 710
receives from the target eNB 730. In that context, a duration between the
time when the UE 710 received the last data packet from the source eNB
720 at 744 to the time when the UE 710 received the first data packet
from the target eNB 730 at 754 may represent a total user plane (U-Plane)
interruption time 764. Moreover, as shown in FIG. 7, the RACH procedure
performed between the UE 710 and the target eNB 730 may be
contention-free or contention-based, which may impact the total C-Plane
handover time 762 and consequently impact the total U-plane interruption
time 764. For example, in a contention-free RACH procedure, the target
eNB 730 generally allocates a Random Access Preamble from a reserved pool
such that no collisions will occur. In contrast, in a contention-based
RACH procedure, multiple UEs may attempt to connect to the target eNB 730
at the same time such that collisions may occur in the event that
multiple UEs transmit the same Preamble identifier. As such, in various
embodiments, whether the RACH procedure performed at 748 is
contention-free or contention-based may impact the total C-Plane handover
time 762 and the total U-Plane interruption time 764. For example,
minimum, mean, and maximum U-Plane interruption times 764 that may occur
in X2 based intra-LTE handovers that use a contention-based or a
contention-free RACH procedure are shown below in Table 2.

[0083] Accordingly, in the exemplary intra-LTE handover shown in FIG. 7,
the total U-Plane interruption time 764 can have a substantial effect on
continuity, packet delay, packet loss, user experience, and/or other
aspects associated with a real-time session, which may further depend on
whether a contention-based or contention-free RACH procedure is used to
synchronize the UE 710 to the target eNB 730. Moreover, the total U-Plane
interruption time 764 typically increases in handovers where the UE 710
switches from a current access network that implements a first radio
access technology (RAT) to a target access network that implements a
different RAT (i.e., "inter-RAT" handovers), and the total U-Plane
interruption time 764 may also increase in inter-system handovers (e.g.,
between 3GPP and non-3GPP accesses). For example, various inter-RAT
handover types and inter-system handover types that may cause session
interruption, packet delay, packet loss, and otherwise degrade user
experience during a VoIP session or other real-time multimedia session
are defined below in Table 3.

[0084] Referring now to FIG. 8, an exemplary signaling call flow
associated with an E-UTRAN to UTRAN intra-RAT handover is illustrated to
demonstrate how inter-RAT and inter-system handovers may interfere with
VoIP or other real-time multimedia sessions. More particularly, as shown
in FIG. 8, an inter-RAT handover from a source access network to a target
access network may be initiated at 842 (i.e., from E-UTRAN to UTRAN in
the illustrated example), at which time uplink and downlink user data may
be transmitted via a bearer between the UE 810 and a source eNB 820 and
one or more GTP tunnels between the source eNB 820 and one or more core
network entities (not shown). In various embodiments, at 844, the source
eNB 820 may then send a handover required message to a source MME 825 to
request that the core network establish resources in the target access
network 830. In various embodiments, the source MME 825 may then
determine that the handover type is an inter-RAT handover to UTRAN from
information in the handover required message from the source eNB 820 that
identifies the target RNC 830. Accordingly, the source MME 825 then
initiates a handover resource allocation procedure at 846, which may
include sending a relocation request message to the target SGSN 835.

[0085] At 848, the target SGSN then relays the relocation request message
to the target RNC 830 to establish the radio network resources (e.g.,
radio access bearers) for the UE 810 in the target RNC 830. For example,
for each radio access bearer (RAB) that the target SGSN 835 requests be
established, the relocation request message sent at 848 may include a RAB
identifier, one or more RAB parameters, a transport layer address (e.g.,
the S-GW address for user plane data where a direct tunnel is used or the
SGSN address where a direct tunnel is not used), and a transport
association (e.g., an uplink Tunnel Endpoint Identifier Data (TEID) in
the S-GW or SGSN). Accordingly, at 848, the target RNC 830 allocates the
requested resources and returns the applicable parameters to the target
SGSN 835 in a relocation request acknowledgement message, wherein the
target RNC 830 may be prepared to receive downlink GTP PDUs from the S-GW
(or the target SGSN 835 where a direct tunnel is not used) for the
accepted RABs upon sending the relocation request acknowledgement message
to the target SGSN 835. In various embodiments, at 850, the target SGSN
835 may send a relocation response message to the source ME 825, wherein
the relocation response message may indicate whether a new S-GW has been
selected, a destination tunnel endpoint for data forwarding in the target
RNC 830, one or more data forwarding parameters depending on whether
direct or indirect forwarding applies, and/or other suitable information
to assist in relocating the UE 810 to the target RNC 830.

[0086] In various embodiments, the signaling that occurs from 842 through
850 generally relates to a preparation phase in the inter-RAT handover
from E-UTRAN to UTRAN. Accordingly, uplink and downlink PDUs may continue
to be transmitted between the UE 810 and the source eNB 820 until the
source MME 825 sends a handover command to the source eNB 820 at 854 to
complete the inter-RAT handover preparation phase towards the source eNB
820. Accordingly, an uplink and/or downlink PDU transmitted at 852 may
represent the last data packet that the UE 810 sends to and/or receives
from the source eNB 820, which initiates data forwarding to the target
RNC 830 or alternatively via the S-GW (not shown) as decided by the
source MME 825 and/or the target SGSN 835 during the handover preparation
phase.

[0087] Furthermore, at 856, the source eNB 820 may send a handover command
to the UE 810 to trigger the handover to the target radio access network,
wherein the handover command sent to the UE 810 may include various
parameters that the target RNC 830 established during the preparation
phase. In response to receiving the handover command from the source eNB
820, the UE 810 may associate one or more bearer IDs with the respective
RABs and suspend transmitting user plane data on an uplink. In various
embodiments, at 858, the UE 810 moves to the target UTRAN (3G) system and
executes the inter-RAT handover according to the parameters provided in
the handover command message received at 856, wherein the inter-RAT
handover from the source E-UTRAN to the target UTRAN may be complete once
the UTRAN access procedures are successfully completed at 858, whereby a
duration between the time when the UE 810 received the handover command
from the source eNB 820 to the time when the UE 810 successfully
completed the UTRAN access procedures may represent a total control plane
(C-Plane) inter-RAT handover time 872.

[0088] At that time, the UE 810 may resume transmitting uplink user plane
data at 862 on one or more Network Layer Access Point Identifiers
(NSAPIs) having radio resources allocated in the target RNC 830. However,
the source eNB 820 may continue to receive downlink user plane PDUs at
860, which the source eNB 820 may relay to either the target RNC 830
where direct forwarding applies or to the source S-GW that then further
relays the downlink user plane PDUs to the target RNC 830 via a target
S-GW where indirect forwarding applies. In either case, at 864, the
target RNC 830 may send a relocation complete message to the target SGSN
835 to indicate that the relocation from the source E-UTRAN to the target
UTRAN completed, at which time the target SGSN 835 may be prepared to
receive data from the target RNC 830 and forward each received uplink PDU
directly to the S-GW. In various embodiments, at 866, the target SGSN 835
may inform the source MME 825 that the UE 810 arrived on the target
access network through a relocation complete notification and the source
MME 825 may further send a message to the target SGSN 835 to acknowledge
the information included in the relocation complete notification.
Furthermore, in various embodiments, the source MME 825 may start a timer
to supervise when to release resources in the source eNB 820 and the
source S-GW (if the S-GW was relocated). For example, when the timer
expires, the source MME 825 generally releases all bearer resources
allocated to the UE 810 and further deletes any EPS bearer resources if
the S-GW was relocated, and upon receiving the relocation complete
acknowledgement message, the target SGSN 835 may start a timer if the
target SGSN 835 allocated S-GW resources for indirect forwarding.

[0089] In various embodiments, the target SGSN 835 may then complete the
inter-RAT handover procedure, which may include sending a modify bearer
request message to the S-GW at 868 in order to inform the S-GW that the
target SGSN 835 now manages all EPS bearer contexts that the UE 810 has
established. The S-GW may then communicate with a PDN GW to coordinate
modifying the bearers associated with the UE 810 and subsequently
transmit a modify bearer response to the target SGSN 835 to acknowledge
that the user plane switch successfully completed and that the user plane
path has been established for all EPS bearer contexts between the UE 810,
the target RNC 830, the target SGSN 835 (where a direct tunnel is not
used), the S-GW, and the PDN GW. Accordingly, the UE 810 may receive a
first downlink PDU from the target RNC 730 at 870, whereby a duration
between the time when the UE 810 received the last PDU from the source
eNB 820 at 852 to the time when the UE 810 received the first PDU from
the target RNC 830 at 870 may represent a total user plane (U-Plane)
interruption time 874. Accordingly, due at least in part to the
substantial signaling between the source access network and the target
access network required to complete the inter-RAT handover, substantial
U-Plane interruption time 874 may occur in inter-RAT and inter-system
handovers. Additional detail relating to the inter-RAT handover procedure
shown in FIG. 8 can be found in 3GPP Technical Specification 23.401.

[0090] Accordingly, to reduce the potential negative effects and the
interruption, packet delay, packet loss, and degraded user experience
that handovers can cause during VoIP sessions or other real-time
multimedia sessions, the various embodiments described in further detail
herein may utilize characteristics associated with PTT sessions and/or
full-duplex VoIP sessions to obtain user behavior statistics that can be
used to determine whether and/or when to trigger a handover. For example,
according to various embodiments, FIG. 9 illustrates an exemplary group
communication platform 900 that can be used to control handovers during a
PTT and/or full-duplex VoIP session.

[0091] More particularly, according to various embodiments, the group
communication platform 900 shown in FIG. 9 includes a Mobile Station
Modem (MSM) 910 and various software layers that are generally "layered"
above the MSM 910. For example, as shown in FIG. 9, the various software
layers in the group communication platform 900 may include Advanced
Mobile Subscriber Software (AMSS) 920 "layered" above the MSM 910, a
mobile operating system layer 930 (e.g., implementing the BREW®
software platform mentioned above) layered above the AMSS 920, and an
application layer above the mobile operating system layer 930, wherein
the application layer may generally include a handover control module
940, a PTT client 950, a group media client 960, and other PTT-aware
applications 970. Accordingly, the various software layers in the group
communication platform 900 may drive an underlying chipset associated
with the MSM 910 and implement a CDMA communication technologies suite
that includes CDMA2000 1× and CDMA2000 1xEV-DO according to a
software protocol stack. For example, in one embodiment, the mobile
operating system layer 930 may provide one or more application
programming interfaces (APIs) for chip-specific and/or device-specific
operations and further provide an isolation layer that eliminates direct
contact with the AMSS 920 and any OEM software on the group communication
platform 900. Furthermore, the mobile operating system layer 930 enables
application development that uses mobile device features without having
to rewrite the application each time a new release of the device-specific
software is released. However, those skilled in the art will appreciate
that the group communication platform 900 can alternatively implement the
various embodiments disclosed herein using other software configurations
(e.g., Linux®, Windows®, or other operating systems or
architectures).

[0092] According to various embodiments, the PTT client 950 may generally
comprise an application that may offer access to PTT services through an
external and/or internal interface (e.g., a PTT-aware user interface). In
general, the PTT client 950 may include all the functionality that
applications may require to run on the mobile operating system 930, such
as the handover control module 940 and the group media client 960. In
addition to providing access to PTT services, the PTT client 950 may
provide a layer to isolate all PTT-aware applications 970 and interfaces
to a group communication server or other network-side components. As
such, in one embodiment, the PTT client 950 may maintain access to PTT
services, respond to group communication requests, process all requests
that relate to PTT services from the PTT-aware applications 970, process
all outgoing PTT requests, collect and package vocoder data packets
associated with originated PTT talk spurts, parse vocoder data packets
associated with terminated PTT talk spurts, and detect mutual silence
that occurs between the time when a PTT talk spurt ends and a new PTT
talk spurt begins.

[0093] According to various embodiments, the group media client 960 may
comprise a mobile operating system-based application that extends PTT
services to media types other than traditional half-duplex voice
communications (e.g., full-duplex VoIP sessions). As such, the group
media client 960 may provide access to group media services through the
external and/or internal PTT-aware user interface. For example, in
various embodiments, the PTT-aware user interface may comprise a mobile
operating system-based application or an application used in combination
with an interface to the AMSS 920. In general, the PTT-aware user
interface may invoke the appropriate APIs (e.g., APIs associated with
other resident PTT-aware applications 970) in response to user requests
that may relate to group-directed media services. The group media client
960 may thereby service the user requests and inform the user about the
result associated with any group-directed media requests.

[0094] According to various embodiments, as noted above, the software
layers included in the group communication platform 900 shown in FIG. 9
may further include a handover control module 940 that can be used to
determine whether and/or when to trigger a handover during a PTT or
full-duplex voice communication session, wherein the handover control
module 940 may communicate with the PTT client 950, the group media
client 960, and the other PTT-aware applications 970 to support services
that relate to handovers during PTT and/or full-duplex voice
communication sessions. More particularly, in various embodiments, the
handover control module 940 that may collect and store statistics that
can be consulted to control whether and/or when to trigger a handover
during a PTT and/or full-duplex VoIP session according to user behavior
during past half-duplex (e.g., PTT) and/or full-duplex VoIP sessions
between a "parent" user (i.e., the user who owns or is otherwise
associated with a device implementing the group communication platform
900) and various target users. Furthermore, the handover control module
940 may collect and store statistics that relate to average switching
delays that occurred during different handover types at different
locations, which the handover control module 940 may compare against the
user behavior statistics to determine whether and/or when to trigger a
handover (if necessary).

[0095] For example, according to various embodiments, FIG. 10 illustrates
an exemplary timing diagram corresponding to a PTT and/or full-duplex
voice communication session between a parent user and a target user,
wherein the handover control module 940 may monitor mutual silence and/or
talk bursts between the parent user and the target user to collect
statistics that can be used to control handover during the voice
communication session and/or subsequent voice communication sessions
between the parent user and the target user. More particularly, referring
to the timing diagram shown in FIG. 10, the handover control module 940
may determine when one or more talk spurts 1012 from the parent user and
determine when one or more talk spurts 1014 from the target user end,
which may further indicate times when mutual silence periods 1016 start
and trigger points 1018 to initiate a handover (if needed). For example,
in various embodiments, the handover control module 940 may determine
when the parent user talk spurts 1012 and the target user talk spurts
1014 end according to an explicit signaling message (e.g., a Media Burst
Control Protocol (MBCP) message as utilized in the Open Mobile Alliance
Push to talk over Cellular (OMA POC) architecture). In another example,
the handover control module 940 may determine when the parent user talk
spurts 1012 and the target user talk spurts 1014 end according to
"marker" bits that can be set in Real-Time Transport Protocol (RTP)
packets to indicate when the parent user talk spurts 1012 and/or the
target user talk spurts 1014 end. In any case, the handover control
module 940 may determine an average duration associated with the parent
user talk spurts 1012, an average duration associated with the target
user talk spurts 1014, and an average duration associated with the mutual
silence periods 1016. Furthermore, the handover control module 940 may
determine how many times the parent user and the target user took the
floor during the voice communication session (four times and three times,
respectively, in the example shown in FIG. 10). Accordingly, the handover
control module 940 may then update statistics in a user behavior table to
track characteristics associated with voice communication sessions
between the parent user and the target user. For example, as shown in
Table 4, the user behavior table may store statistics based on past PTT
and/or full-duplex voice communication sessions between the parent user
and each target user in a contact list associated with the parent user
that has participated in one or more past voice communication sessions
with the parent user, and the average statistics across existing target
users may be calculated and used with respect to new target users that
have not participated in a past voice communication session with the
parent user.

[0096] Accordingly, in various embodiments, the handover control module
940 may track and store statistics that relate to how often the parent
user (i.e., the user who owns the device that may potentially be subject
to a handover) took the floor in PTT sessions with each individual target
user and how often the parent user spoke in full-duplex sessions with
each individual target user, and may likewise track and store statistics
that relate to how often each individual target user took the floor in
the PTT sessions with the parent user and how often each individual user
spoke in the full-duplex sessions with the parent user. Furthermore, the
handover control module 940 may track and store statistics that relate to
average durations associated with talk spurts from the parent user, talk
spurts from each individual target user, and mutual silence periods
during the PTT and full-duplex sessions between the parent user and each
individual target user. Accordingly, after each PTT and/or full-duplex
session between the parent user and one or more target users ends, the
statistics stored in the user behavior table may be updated according to
the characteristics associated with that session (e.g., how many times
the parent user and the target user took the floor or spoke during the
session, average mutual silence durations in between turns speaking,
etc.). Furthermore, as noted above, the average statistics across all
existing target users may be calculated and used with respect to any new
target users that have not previously participated in a PTT and/or
full-duplex session with the parent user during the first PTT and/or
full-duplex session with the new target users, whereby after the first
PTT and/or full-duplex session with the new target users end, new entries
may be added to the user behavior table to store statistics relating to
the new target users based on behavior during the first session.

[0097] Furthermore, in various embodiments, the handover control module
940 may collect and store statistics that relate to average switching
delays during different handover types at different locations, which may
be compared against the user behavior statistics to determine whether
and/or when to trigger a handover if needed. For example, as shown in
Table 5 below, the handover control module 940 may maintain statistics
that relate to the average delay that occurred when switching from a
current radio access technology (RAT) to a target RAT during inter-RAT
handovers at particular locations and when switching from a source eNB to
a target eNB during intra-RAT handovers, wherein depending on any
optimizations that radio access network (RAN) operators may offer, the
average switching delays shown in Table 5 may follow a pattern where
D1<D2<D3 and so on. Furthermore, although the
switching delays shown in Table 5 do not specifically list handovers to
and/or from non-3GPP access networks (e.g., CDMA2000, Wi-Fi, etc.), those
skilled in the art will appreciate that such handover types may be
readily accounted for and suitably incorporated into the handover
statistics used to determine whether and/or when to trigger a handover.

[0098] Accordingly, to determine whether and/or when to trigger a
handover, the handover control module 940 may generally consult the
statistics in the user behavior table and the handover table to determine
a handover trigger point, if needed. For example, according to various
embodiments, FIG. 11 illustrates an exemplary method 1100 in which mutual
silence and/or talk burst statistics may be utilized to determine a
handover trigger point during a PTT session, wherein the method 1100
shown in FIG. 11 may generally be performed using the statistics in the
user behavior table and the statistics in the handover table.

[0099] In particular, the parent user may be engaged in a PTT and/or
full-duplex voice communication session with one or more target users at
block 1110, and a handover process may be started at block 1120 due to
mobility conditions, radio conditions, cell capacity, more favorable
conditions in a neighbor cell, or other suitable conditions. In various
embodiments, at block 1130, the statistics in the user behavior table
stored on the device associated with the parent user may be consulted at
block 1130 to identify a more frequent talker among the parent user and
the target users. For example, referring to the example statistics
provided above in Table 4, Alice historically takes the floor more often
than the parent user, Jane does not take the floor that often compared to
the parent user, and Jill takes the floor at approximately the same
frequency as the parent user. As such, in a voice communication session
with Alice, block 1130 may identify Alice as the more frequent talker,
whereby the handover may be triggered after the next talk spurt from
Alice finishes. On the other hand, in a voice communication session with
Jane, block 1130 may identify the parent user as the more frequent
talker, whereby the handover may be triggered after the next talk spurt
from the parent user finishes. However, in a voice communication session
with Jill, neither the parent user nor Jill may be identified at block
1130 because both users take the floor at approximately the same
frequency, whereby the handover may be triggered after the next talk
spurt from either the parent user or Jill.

[0100] Accordingly, in response to having appropriately identified the
more frequent talker among the parent user and the target users involved
in the voice communication session, whether the talk spurt from the
identified user has finished may be determined at block 1140. After the
talk spurt from the identified user finishes, a determination may be made
as to whether the average mutual silence between the parent user and the
target users can be deemed adequate to support the current handover type.
For example, at block 1150, the handover statistics table may be
consulted to determine the average switching delay associated with the
current handover type based on the current location associated with the
device subject to the handover, wherein the average switching delay
associated with the current handover type may be compared against the
average mutual silence period between the parent user and the target
user. For example, referring again to the example statistics provided
above in Table 4, the average mutual silence between Alice and the parent
user historically lasts about five seconds, which may be adequate to
proceed with any handover type, the average mutual silence between Jane
and the parent user historically lasts about three seconds, which may be
adequate to proceed with intra-RAT handovers, and the average mutual
silence between Jill and the parent user historically lasts about four
seconds, which may be adequate to proceed with most handover types. As
such, in response to determining at block 1150 that the average mutual
silence between the parent user and the target user exceeds the average
switching delay associated with the current handover type, the average
mutual silence may be deemed adequate and the current handover can
proceed accordingly at block 1160 after the triggering talk spurt has
finished. Otherwise, in the event that the average mutual silence between
the parent user and the target user does not exceed the average switching
delay associated with the current handover type, the average mutual
silence may be inadequate to proceed with the current handover type
(e.g., where the current handover is an inter-RAT handover and the target
user is Jane). In that case, the device subject to the handover may allow
the modem make the handover decision at block 1170 (e.g., based on the
conditions that triggered the handover at block 1120).

[0101] According to various embodiments, FIG. 12 illustrates an exemplary
signaling call flow in which a handover during a PTT session may be
triggered or delayed based on a talk burst queue position status, which
may occur in combination with and/or in an alternative to the handover
control techniques described above based on the statistics that relate to
user behavior and the statistics that relate to handover switching
delays. In particular, the signaling flow shown in FIG. 12 may generally
support queuing talk burst requests received from participants during a
PTT session (e.g., according to the OMA PoC architecture), wherein talk
burst requests that are received from one or more PTT clients while
another PTT client has permission to send a talk burst may be queued. In
that context, the signaling flow shown in FIG. 12 may allow a PTT client
1210 to request a queue position or other status associated with queued
talk burst requests from the PTT client 1210 and/or other PTT clients
(not shown) from a participating PTT server 1220 and/or a controlling PTT
server 1230, which may be configured to mediate the PTT session between
the PTT client 1210 and the other PTT clients.

[0102] For example, in the signaling call flow shown in FIG. 12, the
controlling PTT server 1230 may have granted Alice permission to send a
talk burst at 1242, wherein the controlling PTT server 1230 may receive
media corresponding to the talk burst from Alice at 1244 and forward the
received media to the participating PTT server 1220 at 1246. The
participating PTT server 1220 may then relay the media to the PTT client
1210 associated with Bob at 1248. In various embodiments, Bob may press a
PTT button or otherwise request permission to send a talk burst at 1250,
in response to which the PTT client 1210 associated with Bob may send a
talk burst request to the participating PTT server 1220 at 1252, which
may relay the talk burst request to the controlling PTT server 1230 at
1254. Furthermore, if Bob has permission to request priority levels other
than normal priority, the talk burst request sent at 1250, 1252, and 1254
can include a priority level at which Bob has permission to access.

[0103] In various embodiments, the controlling PTT server 1230 may
determine that Alice has permission to send a talk burst at the time that
the talk burst request is received from the PTT client 1210 associated
with Bob. Accordingly, assuming that Bob does not currently have a talk
burst request in the queue and has not requested to preempt the talk
burst from Alice (or alternatively that Alice has preemptive priority
over Bob in the event that the talk burst request sent at 1250, 1252, and
1254 includes a priority level at which Bob has permission to access),
the controlling PTT server 1230 may queue the talk burst request from Bob
and send a talk burst queue position status message to the PTT client
1210 associated with Bob through the participating PTT server 1220 at
1256, 1258. For example, in various embodiments, the talk burst queue
position status message may indicate the current position that the PTT
client 1210 holds in the talk burst request queue, and may optionally
further indicate the priority level (if any) granted to the talk burst
request from the PTT client 1210.

[0104] Accordingly, Bob may see the current position that the PTT client
1210 holds in the talk burst request queue at 1260 and determine whether
to trigger a handover or delay the handover based thereon. For example,
if the talk burst queue position status indicates that Bob's turn to talk
will occur soon, Bob may command the PTT client 1210 to delay the
handover at 1262. Alternatively, if the talk burst queue position status
indicates that Bob has a low position in the queue and will not have a
turn to talk for a while, Bob may command the PTT client 1210 to trigger
the handover immediately at 1262. In a further example, because Bob can
request the position that other participants hold in the talk burst
queue, the decision about whether to trigger or delay the handover at
1262 may depend on the position that the other participants hold in the
talk burst queue. For example, if an important participant will be
talking next or talking soon (e.g., a boss, co-worker, etc.), the command
at 1262 may delay the handover, whereas if the next few participants that
will be talking are less important, the command sent at 1262 may
immediately trigger or otherwise advance the handover.

[0105] According to various embodiments, FIG. 13 illustrates an exemplary
method 1300 in which a handover during a PTT session may be triggered or
delayed based on a talk burst queue position status (e.g., according to
the signaling call flow shown in FIG. 12). More particularly, the method
1300 may generally be carried out on a wireless device that can operate
in an architecture (e.g., OMA PoC) that supports queuing talk burst
requests received from participants in a PTT session when another
participant in the PTT session has already been granted the floor and/or
permission to send a current talk burst.

[0106] For example, in various embodiments, a PTT server may grant
permission to send a current talk burst to a participant in a PTT session
at some point in time prior to a parent participant in the PTT session
(e.g., a user associated with the wireless device carrying out the method
1300) requesting permission to send a talk burst at block 1310.
Furthermore, in use cases where the parent participant has permission to
request a priority level other than normal, the talk burst requested at
block 1310 may further include a priority level at which the parent
participant has permission to access. In various embodiments, because the
PTT server already granted permission to send a current talk burst to the
other participant in the PTT session, the PTT server may queue the talk
burst requested at block 1310. In a similar respect, in the event that
the talk burst requested at block 1310 specified a priority level at
which the parent participant has permission to access, the PTT server may
queue the requested talk burst if the parent participant did not request
to preempt the talk burst from the other participant, or alternatively if
the other participant has preemptive priority over the parent
participant. In any case, in scenarios where the PTT server queues the
requested talk burst, a talk burst queue position status message may be
received from the PTT server at block 1310, wherein the talk burst queue
position status message may indicate the current position that the parent
participant holds in the talk burst request queue, and may optionally
further indicate the priority level (if any) granted to the talk burst
request from the parent participant.

[0107] Accordingly, in various embodiments, the parent participant may
learn the current position that the requested talk burst holds in the
queue and determine whether to trigger and/or delay a handover based
thereon. For example, in response to determining at block 1320 that the
talk burst queue position status indicates that the parent participant
has an approaching turn to talk, the parent participant may input a
command to delay the handover at block 1340. Alternatively, in response
to determining at block 1320 that the parent participant has a low
position in the queue or otherwise does not have an approaching turn to
talk, the parent participant may further determine at block 1330 whether
the talk burst queue position status message indicates that an important
participant or other participant of interest will be talking next or
talking soon (e.g., a boss, co-worker, etc.). Accordingly, if an
important participant or other participant of interest will be talking
next or talking soon, the parent participant may similarly input a
command to delay the handover at block 1340. Otherwise, where the parent
participant does not have an approaching turn to talk and the next one or
more participants in the queue are not deemed sufficiently important to
delay the handover, the parent participant may input a command to
immediately trigger or otherwise advance the handover at block 1350.

[0108] According to various embodiments, FIG. 14 illustrates an exemplary
signaling call flow that may occur in a PTT session prior to, during, and
after a handover. More particularly, at 1442 and 1444, a parent PTT
client 1410 and a target PTT client 1430 may each transmit a respective
Session Initiation Protocol (SIP) REGISTER message to an application
server 1420, wherein the SIP REGISTER messages may include a current IP
address associated with the parent PTT client 1410 and the target PTT
client 1430 and a Uniform Resource Identifier (URI) at which the parent
PTT client 1410 and the target PTT client 1430 wish to receive calls. At
1446 and 1448, the application server 1420 may transmit a SIP 200 OK
message to the parent PTT client 1410 and the target PTT client 1430 to
indicate that the requests sent at 1442 and 1444 succeeded. In various
embodiments, at 1450, the parent PTT client 1410 may then send a SIP
INVITE message to the application server 1420 to invite the target PTT
client 1430 to participate in a PTT call session, wherein the SIP INVITE
message may include a Session Description Protocol (SDP) user name
associated with the parent PTT client 1410 (e.g., "Bob") in addition to a
port number and Internet Protocol (IP) address associated with the parent
PTT client 1410. At 1452, the application server 1420 may then relay the
SIP INVITE message to the target PTT client 1440, which may return a SIP
200 OK message to the application server 1420 to indicate that the
invitation to participate in the PTT call session was accepted at 1454.
Accordingly, the SIP 200 OK message sent to the application server 1420
may include an SDP user name (e.g., "Alice"), port number, and IP address
associated with the target PTT client 1430. At 1456, the application
server 1420 may then relay the SIP 200 OK message to the parent PTT
client 1410, whereby the parent PTT client 1410 and the target PTT client
1430 may have sufficient information about one another to establish the
PTT call session at 1458.

[0109] In various embodiments, at some subsequent point in time, the
parent PTT client 1410 may initiate a handover 1460 according to the
techniques described in further detail above (e.g., statistics that
relate to whether Bob or Alice historically take the floor more often
during PTT and/or full-duplex voice sessions with one another, an average
mutual silence duration following talk spurts during voice sessions
between Bob and Alice, an average switching delay associated with the
handover to be initiated at 1460, etc.). In various embodiments, after
performing a successful handover to a target radio access technology
(RAT) or target eNB, the existing session parameters that were used to
establish the session at 1458 need to be updated. Accordingly, at 1462,
the parent PTT client 1410 may send a SIP re-INVITE message to the
application server 1420 to update the prior contact information
associated with the media stream (e.g., a new port and new IP address on
the target RAT or target eNB). At 1464, the application server 1420 may
relay the SIP re-INVITE message to the target PTT client 1430, which may
return a SIP 200 OK message to the application server 1420 at 1466 to
indicate that the contact information was successfully updated and to
restate the SDP user name, port number, and IP address associated with
the target PTT client 1430. At 1468, the application server 1420 may
relay the SIP 200 OK message to the parent PTT client 1410, at which time
the parent PTT client 1410 and the target PTT client 1430 may have
sufficient information to resume the media stream.

[0110] According to various embodiments, FIG. 15 illustrates an exemplary
base station 1510 and an exemplary wireless communication device 1520,
which may be any base station and/or wireless communication device that
can communicate with one another during a PTT session in accordance with
the various aspects and embodiments disclosed herein. In this design,
base station 1510 is equipped with T antennas 1534a through 1534t, and
wireless communication device 1520 is equipped with R antennas 1552a
through 1552r, where T and R are generally greater than or equal to one.

[0111] At base station 1510, a transmit processor 1514 may receive data
for unicast services and data for broadcast and/or multicast services
from a data source 1512 (e.g., directly or indirectly from an application
server). Transmit processor 1514 may process the data for each service to
obtain data symbols. Transmit processor 1514 may also receive scheduling
information, configuration information, control information, system
information and/or other overhead information from a controller/processor
1540 and/or a scheduler 1544. Transmit processor 1514 may process the
received overhead information and provide overhead symbols. A transmit
(TX) multiple-input multiple-output (MIMO) processor 1530 may multiplex
the data and overhead symbols with pilot symbols, process (e.g., precode)
the multiplexed symbols, and provide T output symbol streams to T
modulators (MOD) 1532a through 1532t. Each modulator 1532 may process a
respective output symbol stream (e.g., for OFDM) to obtain an output
sample stream. Each modulator 1532 may further process (e.g., convert to
analog, amplify, filter, and upconvert) the output sample stream to
obtain a downlink signal. T downlink signals from modulators 1532a
through 1532t may be transmitted via T antennas 1534a through 1534t,
respectively.

[0112] At wireless communication device 1520, antennas 1552a through 1552r
may receive the downlink signals from base station 1510 and provide
received signals to demodulators (DEMOD) 1554a through 1554r,
respectively. Each demodulator 1554 may condition (e.g., filter, amplify,
downconvert, and digitize) a respective received signal to obtain
received samples and may further process the received samples (e.g., for
OFDM) to obtain received symbols. A MIMO detector 1560 may receive and
process the received symbols from all R demodulators 1554a through 1554r
and provide detected symbols. A receive processor 1570 may process the
detected symbols, provide decoded data for wireless communication device
1520 and/or desired services to a data sink 1572, and provide decoded
overhead information to a controller/processor 1590. In general, the
processing by MIMO detector 1560 and receive processor 1570 is
complementary to the processing by TX MIMO processor 1530 and transmit
processor 1514 at base station 1510.

[0113] On the uplink, at wireless communication device 1520, data from a
data source 1578 and overhead information from a controller/processor
1590 may be processed by a transmit processor 1580, further processed by
a TX MIMO processor 1582 (if applicable), conditioned by modulators 1554a
through 1554r, and transmitted via antennas 1552a through 1552r. At base
station 1510, the uplink signals from wireless communication device 1520
may be received by antennas 1534, conditioned by demodulators 1532,
detected by a MIMO detector 1536, and processed by a receive processor
1538 to obtain the data and overhead information transmitted by wireless
communication device 1520.

[0115] Controller/processor 1590 may implement processes for the
techniques described herein. Memories 1542 and 1592 may store data and
program codes for base station 1510 and wireless communication device
1520, respectively. Accordingly, group communications can be accomplished
in accordance with the various embodiments disclosed herein, while still
remaining compliant with the existing standards.

[0116] According to various embodiments, FIG. 16 illustrates an exemplary
server 1600 (e.g., a group communication server) that may control
communications among various wireless telecommunication devices in a PTT
group. In one example, the server 1600 may be one exemplary configuration
corresponding to the MSC, the DCH, the MCU, and/or any other network
entity described above. As shown in FIG. 16, the server 1600 may include
a processor 1601 coupled to volatile memory 1602 and a large capacity
nonvolatile memory (e.g., a disk drive 1603). The server 1600 may also
include a floppy disc drive, compact disc (CD) or DVD disc drive 1606
coupled to the processor 1601. The server 1600 may also include network
access ports 1604 coupled to the processor 1601 for establishing data
connections with a network 1607, such as a local area network coupled to
other broadcast system computers and servers or to the Internet.
Furthermore, in context with FIG. 5 and/or FIG. 15, those skilled in the
art will appreciate that the server 1600 shown in FIG. 16 may correspond
to one exemplary implementation of the wireless communication devices
500A, 500B, and/or 1520 shown in FIG. 5 and/or FIG. 15, which may
transmit and/or receive information using components that may correspond
to the network access points 1604 used by the server 1600 to communicate
with the network 1607, process information using components that may
correspond to the processor 1601, and store information using components
that may correspond to any combination of the volatile memory 1602, the
disk drive 1603 and/or the disc drive 1606. Accordingly, FIG. 16
generally helps to demonstrate that the wireless communication devices
500A and 500B shown in FIG. 5 and/or the wireless communication device
1520 shown in FIG. 15 may have a server implementation as shown in FIG.
16 and/or a wireless communication device implementation as shown in FIG.
5 and FIG. 15.

[0117] Those skilled in the art will appreciate that information and
signals may be represented using any of a variety of different
technologies and techniques. For example, data, instructions, commands,
information, signals, bits, symbols, and chips that may be referenced
throughout the above description may be represented by voltages,
currents, electromagnetic waves, magnetic fields or particles, optical
fields or particles, or any combination thereof.

[0118] Further, those skilled in the art will appreciate that the various
illustrative logical blocks, modules, circuits, and algorithm steps
described in connection with the aspects disclosed herein may be
implemented as electronic hardware, computer software, or combinations
thereof. To clearly illustrate this interchangeability of hardware and
software, various illustrative components, blocks, modules, circuits, and
steps have been described above generally in terms of their
functionality. Whether such functionality is implemented as hardware or
software depends upon the particular application and design constraints
imposed on the overall system. Skilled artisans may implement the
described functionality in varying ways for each particular application,
but such implementation decisions should not be interpreted to depart
from the scope of the present disclosure.

[0119] The various illustrative logical blocks, modules, and circuits
described in connection with the embodiments disclosed herein may be
implemented or performed with a general purpose processor, a digital
signal processor (DSP), an application specific integrated circuit
(ASIC), a field programmable gate array (FPGA) or other programmable
logic device, discrete gate or transistor logic, discrete hardware
components, or any combination thereof designed to perform the functions
described herein. A general purpose processor may be a microprocessor,
but in the alternative, the processor may be any conventional processor,
controller, microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices (e.g., a combination of
a DSP and a microprocessor, a plurality of microprocessors, one or more
microprocessors in conjunction with a DSP core, etc.).

[0120] The methods, actions, and/or algorithms described in connection
with the embodiments disclosed herein may be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. A software module may reside in RAM memory, flash
memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a
removable disk, a CD-ROM, or any other form of storage medium known in
the art. An exemplary storage medium is coupled to the processor such
that the processor can read information from, and write information to,
the storage medium. In the alternative, the storage medium may be
integral to the processor. The processor and the storage medium may
reside in an ASIC. The ASIC may reside in a user terminal (e.g., UE). In
the alternative, the processor and the storage medium may reside as
discrete components in a user terminal.

[0121] In one or more exemplary embodiments, the functions described may
be implemented in hardware, software, firmware, or any combination
thereof. If implemented in software, the functions may be stored on or
transmitted over as one or more instructions or code on a
computer-readable medium. Computer-readable media includes both computer
storage media and communication media including any medium that
facilitates transfer of a computer program from one place to another. A
storage media may be any available media that can be accessed by a
computer. By way of example, and not limitation, such computer-readable
media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk
storage, magnetic disk storage or other magnetic storage devices, or any
other medium that can be used to carry or store desired program code in
the form of instructions or data structures and that can be accessed by a
computer. Also, any connection is properly termed a computer-readable
medium. For example, if the software is transmitted from a website,
server, or other remote source using a coaxial cable, fiber optic cable,
twisted pair, digital subscriber line (DSL), or wireless technologies
such as infrared, radio, and microwave, then the coaxial cable, fiber
optic cable, twisted pair, DSL, or wireless technologies such as
infrared, radio, and microwave are included in the definition of medium.
Disk and disc, as used herein, includes compact disc (CD), laser disc,
optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc
where disks usually reproduce data magnetically, while discs reproduce
data optically with lasers. Combinations of the above should also be
included within the scope of computer-readable media.

[0122] While the foregoing disclosure shows illustrative aspects of the
disclosure, it should be noted that various changes and modifications
could be made herein without departing from the scope of the disclosure
as defined by the appended claims. The functions, steps and/or actions of
the method claims in accordance with the aspects of the disclosure
described herein need not be performed in any particular order.
Furthermore, although elements of the disclosure may be described or
claimed in the singular, the plural is contemplated unless limitation to
the singular is explicitly stated.